diff --git a/.DS_Store b/.DS_Store
new file mode 100644
index 000000000..8bae2d56e
Binary files /dev/null and b/.DS_Store differ
diff --git a/exercises/B-hello-world/README.md b/exercises/B-hello-world/README.md
index 8c704fb43..67bbfa568 100644
--- a/exercises/B-hello-world/README.md
+++ b/exercises/B-hello-world/README.md
@@ -15,4 +15,7 @@ Inside of `exercise.js` there's a line of code that will print "Hello world!".
 - Try to `console.log()` something different. For example, 'Hello World. I just started learning JavaScript!'.
 - Try to console.log() several things at once.
 - What happens when you get rid of the quote marks?
+I will recive this SyntaxError: missing ) after argument list
+
 - What happens when you console.log() just a number without quotes?
+Just that number will be printed without any error.
diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..68cb82148 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,4 @@
 console.log("Hello world");
+console.log("Hello World. I just started learning JavaScript!");
+console.log("I am so happy to learn new programming language");
+console.log(123);
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..1dd1a4fbe 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `greeting`
-
+let greeting="Hello World"
+console.log(greeting);
+console.log(greeting);
 console.log(greeting);
diff --git a/exercises/D-strings/exercise.js b/exercises/D-strings/exercise.js
index 2cffa6a81..0a862579e 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `message`
-
+let message="This is Laleh";
+let massageType=typeof message;
 console.log(message);
+console.log(massageType);
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..079df8cc4 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,4 @@
 // Start by creating a variable `message`
-
-console.log(message);
+let greeting="Hello, My name is "
+let myName="Laleh.";
+console.log(greeting+myName);
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..a678080dd 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,6 @@
 // Start by creating a variable `message`
+let myName="Laleh";
 
-console.log(message);
+let myNameLength=myName.length;
+
+console.log("My name is " + myName + " and my name is " + myNameLength + " characters long");
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..5838acc78 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,14 @@
-const name = " Daniel  ";
+const myName = " Daniel  ";
+
+
+let myNameLength = myName.length;
+
+console.log(
+  "My name is " +
+    myName.trim() +
+    " and my name is " +
+    myNameLength +
+    " characters long"
+);
+
 
-console.log(message);
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..804cb0370 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,7 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+
+let numberOfStudents=30;
+let numberOfMentors=5;
+let sum = numberOfStudents + numberOfMentors;
+
+console.log(sum);
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..f079a5b7d 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,11 @@
-var numberOfStudents = 15;
-var numberOfMentors = 8;
+let numberOfStudents = 15;
+let numberOfMentors = 8;
+let sum = numberOfStudents+numberOfMentors;
+
+let studentPercentage = (numberOfStudents/sum)*100;
+let MentorsPercentage = (numberOfMentors/sum)*100;
+
+console.log("The percentage of student is " + Math.round(studentPercentage)+"%");
+console.log("The percentage of mentor is " + Math.round(MentorsPercentage)+"%");
+
+
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..53c93cdc2 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,13 @@
-function halve(number) {
+function half(number) {
   // complete the function here
+  return number/2;
 }
 
-var result = halve(12);
+var result = half(12);
+var result1 = half(6);
 
 console.log(result);
+console.log(result1);
+
+
+
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..a57a8d69a 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,5 +1,5 @@
 function triple(number) {
-  // complete function here
+  return number*3;
 }
 
 var result = triple(12);
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..0f66ec66a 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,9 +1,9 @@
 // Complete the function so that it takes input parameters
-function multiply() {
-  // Calculate the result of the function and return it
+function multiply(num1,num2) {
+  return num1*num2;
 }
 
-// Assign the result of calling the function the variable `result`
+
 var result = multiply(3, 4);
 
 console.log(result);
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..3bf7d1e95 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,5 +1,8 @@
 // Declare your function first
 
+function divide(num1,num2){
+    return num1/num2;
+}
 var result = divide(3, 4);
 
 console.log(result);
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..f2497c9e6 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,5 +1,7 @@
 // Write your function here
-
+function createGreeting (name){
+    return "hello my name is "+name
+}
 var greeting = createGreeting("Daniel");
 
 console.log(greeting);
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..35996db85 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,8 @@
 // Declare your function first
-
+function sumFn(num1,num2){
+    return num1+num2;
+}
 // Call the function and assign to a variable `sum`
 
+let sum = sumFn(13, 124);
 console.log(sum);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..3e65b3602 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,5 +1,7 @@
 // Declare your function here
-
+function createLongGreeting(name,age){
+    return "Hello, my name is "+name+ "and I'm "+age+" years old";
+}
 const greeting = createLongGreeting("Daniel", 30);
 
 console.log(greeting);
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..399d5c7af 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -3,3 +3,14 @@ var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function shoutyGreeting(mentorName) {
+  return "hello " + mentorName.toUpperCase();
+}
+
+
+console.log(shoutyGreeting(mentor1));
+console.log(shoutyGreeting(mentor2));
+console.log(shoutyGreeting(mentor3));
+console.log(shoutyGreeting(mentor4));
+console.log(shoutyGreeting(mentor5));
\ No newline at end of file
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index d82e59480..2ebfd1daf 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,22 +5,30 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(priceInPound) {
+  /*let priceInDollar = priceInPound * 1.4;*/
+  return priceInPound * 1.4;
+}
 
 /*
   CURRENCY CONVERSION
   ===================
   The business is now breaking into the Brazilian market
   Write a new function for converting to the Brazilian real (exchange rate is 5.7 BRL to £)
-  They have also decided that they should add a 1% fee to all foreign transactions, which means you only convert 99% of the £ to BRL.
+  They have also decided that they should add a 1% fee to all foreign transactions,
+   which means you only convert 99% of the £ to BRL.
 */
 
-function convertToBRL() {}
+function convertToBRL(priceInPound) {
+  let priceInBrazilian = 0.99 * priceInPound * 5.7;
+
+  return Number(priceInBrazilian.toFixed(2));
+}
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
 
-To run these tests type `npm run extraTo run the tests for just this one file, type `npm run extra-tests -- --testPathPattern 1-syntax-errors` into your terminal
+To run these tests type `npm run extraTo run the tests for just this one file, type `npm test -- --testPathPattern 1-currency-conversion` into your terminal
 (Reminder: You must have run `npm install` one time before this will work!)
 */
 
diff --git a/extra/2-piping.js b/extra/2-piping.js
index 9c8ebc76a..398cec9a4 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,31 +16,39 @@
   the final result to the variable goodCode
 */
 
-function add() {
+function add(num1,num2) {
+  return num1+num2;
 
 }
 
-function multiply() {
-
+function multiply(num1,num2) {
+  return num1*num2;
 }
 
-function format() {
+function format(number) {
+  return "£" + number;
 
 }
 
 const startingValue = 2;
 
+function random(startingValue){
+    return "£" + (startingValue + 10) * 2;
+}
+
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode =
+let badCode = "£" + (startingValue + 10) * 2;
 
 /* BETTER PRACTICE */
+let sum = startingValue + 10;
+let total = sum * 2;
 
-let goodCode =
+let goodCode = "£" + total;
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
 
-To run these tests type `npm run extraTo run the tests for just this one file, type `npm run extra-tests -- --testPathPattern 2-piping` into your terminal
+To run these tests type `npm run extraTo run the tests for just this one file, type `npm test -- --testPathPattern 2-piping` into your terminal
 (Reminder: You must have run `npm install` one time before this will work!)
 */
 
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index f3adbefa5..eb2bf655b 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -43,32 +43,13 @@
     Very doubtful.
 */
 
-// This should log "The ball has shaken!"
-// and return the answer.
-function shakeBall() {
-  //Write your code in here
-}
-
-/* 
-  This function should say whether the answer it is given is
-    - very positive
-    - positive
-    - negative
-    - very negative
-
-  This function should expect to be called with any value which was returned by the shakeBall function.
-*/
-function checkAnswer(answer) {
-  //Write your code in here
-}
-
 /* 
 ==================================
 ======= TESTS - DO NOT MODIFY =====
 
 There are some Tests in this file that will help you work out if your code is working.
 
-To run these tests type `npm run extraTo run the tests for just this one file, type `npm run extra-tests -- --testPathPattern 3-magic-8-ball` into your terminal
+To run these tests type `npm run extraTo run the tests for just this one file, type `npm test -- --testPathPattern 3-magic-8-ball` into your terminal
 (Reminder: You must have run `npm install` one time before this will work!)
 ==================================
 */
@@ -101,7 +82,9 @@ test("magic 8 ball returns different values each time", () => {
     );
   }
 
-  let seenPositivities = new Set(Array.from(seenAnswers.values()).map(checkAnswer));
+  let seenPositivities = new Set(
+    Array.from(seenAnswers.values()).map(checkAnswer)
+  );
   if (seenPositivities.size < 2) {
     throw Error(
       "Expected to random answers with different positivities each time shakeBall was called, but always got the same one"
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..cfd19b968 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,18 @@
 // There are syntax errors in this code - can you fix it to pass the tests?
 
-function addNumbers(a b c) {
+function addNumbers(a,b,c) {
   return a + b + c;
 }
 
-function introduceMe(name, age)
-  return "Hello, my name is " + name "and I am " age + "years old";
+function introduceMe(name, age){
+  return "Hello, my name is " + name +" and I am "+ age + " years old";
+}
+  
 
 function getTotal(a, b) {
-  total = a ++ b;
+  total = a + b;
 
-  return "The total is total";
+  return "The total is "+ total;
 }
 
 /* 
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..4902e77f2 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,16 @@
 // The syntax for this function is valid but it has an error, find it and fix it.
 
 function trimWord(word) {
-  return wordtrim();
+  return word.trim();
 }
 
 function getStringLength(word) {
-  return "word".length();
+  return word.length;
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+  return a * b * c;
+  
 }
 
 /* 
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..dc0265de1 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -2,15 +2,22 @@
 function getRandomNumber() {
   return Math.random() * 10;
 }
+/********************************************************************************** */
+/*Math.random() returns a random number between 0 (inclusive),  and 1 (exclusive)
+/********************************************************************************** */
 
 // Add comments to explain what this function does. You're meant to use Google!
 function combine2Words(word1, word2) {
   return word1.concat(word2);
 }
+/********************************************************************************** */
+/*The concat() method joins two or more strings
+/********************************************************************************** */
 
 function concatenate(firstWord, secondWord, thirdWord) {
   // Write the body of this function to concatenate three words together.
   // Look at the test case below to understand what this function is expected to return.
+  return firstWord+" ".concat(secondWord)+" ".concat(thirdWord);
 }
 
 /* 
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..e8b91c384 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,11 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(itemPrice) {
+  let tax = itemPrice * 0.2;
+  let total=tax+itemPrice;
+  return total;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +21,11 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(itemPrice) {
+  let totalPrice = calculateSalesTax(itemPrice);
+  let formatPrice = "£" + totalPrice.toFixed(2);
+  return formatPrice;
+}
 
 /* 
 ===================================================
diff --git a/package.json b/package.json
index 93e0861e3..ff48de45a 100644
--- a/package.json
+++ b/package.json
@@ -14,21 +14,27 @@
     "url": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1/issues"
   },
   "jest": {
-    "setupFilesAfterEnv": ["jest-extended"],
+    "setupFilesAfterEnv": [
+      "jest-extended"
+    ],
     "projects": [
       {
         "displayName": "mandatory",
-        "testMatch": ["<rootDir>/mandatory/*.js"]
+        "testMatch": [
+          "<rootDir>/mandatory/*.js"
+        ]
       },
       {
         "displayName": "extra",
-        "testMatch": ["<rootDir>/extra/*.js"]
+        "testMatch": [
+          "<rootDir>/extra/*.js"
+        ]
       }
     ]
   },
   "homepage": "https://github.com/CodeYourFuture/JavaScript-Core-1-Coursework-Week1#readme",
   "devDependencies": {
     "jest": "^26.6.3",
-    "jest-extended": "^0.11.5"
+    "jest-extended": "^1.2.0"
   }
 }