diff --git a/exercises/B-hello-world/exercise.js b/exercises/B-hello-world/exercise.js
index b179ee953..017a3123e 100644
--- a/exercises/B-hello-world/exercise.js
+++ b/exercises/B-hello-world/exercise.js
@@ -1 +1,4 @@
 console.log("Hello world");
+console.log("Are you learning as well?");
+console.log("I " + "hope " + "that you know " + "what you are doing.");
+console.log(3);
diff --git a/exercises/C-variables/exercise.js b/exercises/C-variables/exercise.js
index a6bbb9786..3244c32f2 100644
--- a/exercises/C-variables/exercise.js
+++ b/exercises/C-variables/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `greeting`
-
+var 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..11b1e4b1f 100644
--- a/exercises/D-strings/exercise.js
+++ b/exercises/D-strings/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `message`
-
+var message = "This is a string";
 console.log(message);
+var messageType = typeof message;
+console.log(messageType);
diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..e15251fc8 100644
--- a/exercises/E-strings-concatenation/exercise.js
+++ b/exercises/E-strings-concatenation/exercise.js
@@ -1,3 +1,5 @@
 // Start by creating a variable `message`
-
+var firstPart = "Hello, my name is ";
+var secondPart = "Ro.";
+var message = firstPart + secondPart;
 console.log(message);
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..6609cb1fe 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,18 @@
 // Start by creating a variable `message`
-
+var name = "Daniel";
+var nameLength = name.length;
+var messagePart;
+if (name.length === 1) {
+  var messagePart = "character";
+} else {
+  var messagePart = "characters";
+}
+var message =
+  "My name is " +
+  name +
+  " and my name is " +
+  nameLength +
+  " " +
+  messagePart +
+  " long.";
 console.log(message);
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..0b0b66a5f 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,18 @@
 const name = " Daniel  ";
-
+var noSpaceName = name.trim();
+var nameLength = noSpaceName.length;
+var messagePart;
+if (noSpaceName.length === 1) {
+  var messagePart = "character";
+} else {
+  var messagePart = "characters";
+}
+var message =
+  "My name is " +
+  noSpaceName +
+  " and my name is " +
+  nameLength +
+  " " +
+  messagePart +
+  " long.";
 console.log(message);
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..b787d49bb 100644
--- a/exercises/G-numbers/exercise.js
+++ b/exercises/G-numbers/exercise.js
@@ -1 +1,9 @@
 // Start by creating a variables `numberOfStudents` and `numberOfMentors`
+let numberOfStudents = 15;
+let numberOfMentors = 8;
+console.log("Number of students: " + numberOfStudents);
+console.log("Number of mentors: " + numberOfMentors);
+console.log(
+  "Total number of students and mentors: " +
+    (numberOfStudents + numberOfMentors)
+);
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..f88fe01b8 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,11 @@
 var numberOfStudents = 15;
 var numberOfMentors = 8;
+let total = numberOfStudents + numberOfMentors;
+function percentageOf(num) {
+  var precisePercentage = (num / total) * 100;
+  let roughPercentage = Math.round(precisePercentage);
+  return roughPercentage;
+}
+
+console.log("Percentage students: " + percentageOf(numberOfStudents) + "%");
+console.log("Percentage mentors: " + percentageOf(numberOfMentors) + "%");
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..99898ae3c 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,4 +1,5 @@
 function halve(number) {
+  return number / 2;
   // complete the function here
 }
 
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..75d1c2f90 100644
--- a/exercises/J-functions/exercise2.js
+++ b/exercises/J-functions/exercise2.js
@@ -1,4 +1,5 @@
 function triple(number) {
+  return number * 3;
   // complete function here
 }
 
diff --git a/exercises/K-functions-parameters/exercise.js b/exercises/K-functions-parameters/exercise.js
index 8d5db5e69..cb0b0d927 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,5 +1,6 @@
 // Complete the function so that it takes input parameters
-function multiply() {
+function multiply(num1, num2) {
+  return num1 * num2;
   // Calculate the result of the function and return it
 }
 
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..8f0f0680b 100644
--- a/exercises/K-functions-parameters/exercise2.js
+++ b/exercises/K-functions-parameters/exercise2.js
@@ -1,5 +1,7 @@
 // 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..8aaea4624 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,5 +1,9 @@
 // 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..0e5a78614 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,9 @@
 // Declare your function first
+function add(num1, num2) {
+  return num1 + num2;
+}
 
 // Call the function and assign to a variable `sum`
+let sum = add(13, 124);
 
 console.log(sum);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..1b8bd1499 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,5 +1,17 @@
 // Declare your function here
 
-const greeting = createLongGreeting("Daniel", 30);
+function createLongGreeting(name, age) {
+  let ageGreet;
+  if (age === 1) {
+    ageGreet = "year";
+  } else {
+    ageGreet = "years";
+  }
+  return (
+    "Hello, my name is " + name + " and I'm " + age + " " + ageGreet + " old"
+  );
+}
+
+const greeting = createLongGreeting("Daniel", 20);
 
 console.log(greeting);
diff --git a/exercises/L-functions-nested/exercise.js b/exercises/L-functions-nested/exercise.js
index a5d377442..b8449b254 100644
--- a/exercises/L-functions-nested/exercise.js
+++ b/exercises/L-functions-nested/exercise.js
@@ -3,3 +3,13 @@ var mentor2 = "Irina";
 var mentor3 = "Mimi";
 var mentor4 = "Rob";
 var mentor5 = "Yohannes";
+
+function shoutGreeting(name) {
+  return "HELLO " + name.toUpperCase();
+}
+
+console.log(shoutGreeting(mentor1));
+console.log(shoutGreeting(mentor2));
+console.log(shoutGreeting(mentor3));
+console.log(shoutGreeting(mentor4));
+console.log(shoutGreeting(mentor5));
diff --git a/extra/1-currency-conversion.js b/extra/1-currency-conversion.js
index d82e59480..9a94f4b1a 100644
--- a/extra/1-currency-conversion.js
+++ b/extra/1-currency-conversion.js
@@ -5,7 +5,9 @@
   Write a function that converts a price to USD (exchange rate is 1.4 $ to £)
 */
 
-function convertToUSD() {}
+function convertToUSD(num) {
+  return num * 1.4;
+}
 
 /*
   CURRENCY CONVERSION
@@ -15,12 +17,15 @@ function convertToUSD() {}
   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(num) {
+  let result = num * 0.99 * 5.7;
+  return Number(result.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 run extra-tests -- --testPathPattern 1-syntax-errors` correct path: `npm run extra-tests -- --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..a673525ad 100644
--- a/extra/2-piping.js
+++ b/extra/2-piping.js
@@ -16,26 +16,26 @@
   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(num) {
+  return "£" + num;
 }
 
 const startingValue = 2;
 
 // Why can this code be seen as bad practice? Comment your answer.
-let badCode =
+let badCode = format(24);
 
 /* BETTER PRACTICE */
 
-let goodCode =
+let goodCode = format(24);
 
 /* ======= TESTS - DO NOT MODIFY ===== 
 There are some Tests in this file that will help you work out if your code is working.
diff --git a/extra/3-magic-8-ball.js b/extra/3-magic-8-ball.js
index f3adbefa5..02a03b72c 100644
--- a/extra/3-magic-8-ball.js
+++ b/extra/3-magic-8-ball.js
@@ -43,9 +43,41 @@
     Very doubtful.
 */
 
+
+
 // This should log "The ball has shaken!"
 // and return the answer.
 function shakeBall() {
+
+  listOfAnswers = [
+  "It is certain",
+  "It is decidedly so.",
+  "Without a doubt.",
+  "Yes - definitely.",
+  "You may rely on it.",
+  "As I see it, yes.",
+  "Most likely.",
+  " Outlook good.",
+  "Yes.",
+  "Signs point to yes.",
+  "Reply hazy, try again.",
+  "Ask again later.",
+  "Better not tell you now.",
+  "Cannot predict now.",
+  "Concentrate and ask again.",
+  "Don't count on it.",
+  "My reply is no.",
+  "My sources say no.",
+  "Outlook not so good.",
+  "Very doubtful.",
+];
+
+var randomNumber = Math.floor(Math.random() * 20);
+
+  console.log("The ball has shaken!");
+
+  var answer = listOfAnswers[randomNumber];
+  return answer;
   //Write your code in here
 }
 
@@ -59,6 +91,17 @@ function shakeBall() {
   This function should expect to be called with any value which was returned by the shakeBall function.
 */
 function checkAnswer(answer) {
+  var shortMessage;
+  if (listOfAnswers.indexOf(answer) >= 0 && listOfAnswers.indexOf(answer) <= 4 ) {
+    shortMessage = "very positive";
+  } else if (listOfAnswers.indexOf(answer) >= 5 && listOfAnswers.indexOf(answer) <= 9) {
+    shortMessage = "positive";
+  } else if (listOfAnswers.indexOf(answer) >= 10 && listOfAnswers.indexOf(answer) <= 14) {
+    shortMessage = "negative";
+  } else if (listOfAnswers.indexOf(answer) >= 15 && listOfAnswers.indexOf(answer) <= 19) {
+    shortMessage = "very negative";
+  }
+  return shortMessage;
   //Write your code in here
 }
 
@@ -101,7 +144,9 @@ 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..98360ac6b 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,17 @@
 // 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..37c4ebc15 100644
--- a/mandatory/2-logic-error.js
+++ b/mandatory/2-logic-error.js
@@ -1,16 +1,15 @@
 // 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..d5ab20241 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -1,9 +1,13 @@
 // Add comments to explain what this function does. You're meant to use Google!
+/*The Math.random() function returns a floating-point, pseudo-random number in the range 0 to less than 1 (inclusive of 0, but not 1) with approximately uniform distribution over that range — which you can then scale to your desired range. The implementation selects the initial seed to the random number generation algorithm; it cannot be chosen or reset by the user.*/
+/*this function create random number, the result is random number time by 10*/
 function getRandomNumber() {
   return Math.random() * 10;
 }
 
 // Add comments to explain what this function does. You're meant to use Google!
+/*The concat() method concatenates the string arguments to the calling string and returns a new string.*/
+/*this function is going to create connected word from word1 and word2 input*/
 function combine2Words(word1, word2) {
   return word1.concat(word2);
 }
@@ -11,6 +15,7 @@ function combine2Words(word1, word2) {
 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 + " " + thirdWord);
 }
 
 /* 
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..f7aeb85f2 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,10 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(num) {
+  let result = num + num * 0.2;
+  return result;
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +20,10 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(num) {
+  let result = num + num * 0.2;
+  return "£" + result.toFixed(2);
+}
 
 /* 
 ===================================================