diff --git a/problems/problem1.js b/problems/problem1.js
index 6d7505c..9917591 100644
--- a/problems/problem1.js
+++ b/problems/problem1.js
@@ -2,16 +2,17 @@ var assert = require('assert');
 
 // we need 5 test cases. I provided 1 input
 let inputs = [
-  ""
+  "aa", '_as', '1111', 'blue', ""
 ]
 
 let outputs = [
-  
+  'a', '_', '1', 'b', undefined
 ]
 
-// Make this function return the first letter of the string that is passed to it. If the string does not have a first letter, return undefined
+// Make this function return the first character of the string that is passed to it. If the string does not have a first letter, return undefined
 function f(str) {
-    
+  if (str.length == 0) return undefined;
+  return str[0];
 }
 
 function runTest(i) {
diff --git a/problems/problem10.js b/problems/problem10.js
index e7eddde..4de59d6 100644
--- a/problems/problem10.js
+++ b/problems/problem10.js
@@ -2,11 +2,11 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  
+  "we are one", "the three musquaqueers", 'true gods of what?', 'power user', 'POP POP LOL'
 ]
 
 let outputs = [
-  
+  'We Are One', 'The Three Musquaqueers', 'True Gods Of What?', 'Power User', 'Pop Pop Lol'
 ]
 
 /*
@@ -17,7 +17,16 @@ f("ALL YOUR BASE ARE BELONG"); // All Your Base Are Belong
 
 */
 function f(str) {
-    
+    var lower = str.toLowerCase();
+    var splitStr = lower.split(" ");
+    var toUpper = [];
+    for (var i= 0; i < splitStr.length; i++) {
+        var firstLetter = splitStr[i][0];                               
+        firstLetter = firstLetter.toUpperCase();                              // ALWAYS ASSIGN THE NEW VALUE TO THE VARIABLE!!!
+        splitStr[i] = firstLetter + splitStr[i].substring(1);
+        toUpper.push(splitStr[i]);
+    }
+    return toUpper.join(" ");
 }
 
 function runTest(i) {
diff --git a/problems/problem11.js b/problems/problem11.js
index a9db8bc..bac3e63 100644
--- a/problems/problem11.js
+++ b/problems/problem11.js
@@ -2,18 +2,31 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  
+  [2, 3, 4],
+  [10, 5, 15, 20],
+  ['a', 10,'c', 3, 'b'],
+  [undefined, 11, 12 ],
+  []
+
 ]
 
 let outputs = [
-  
+  9, 50, 13, 23, 0
 ]
 
 /*
 Make this function return the sum of all the numbers in the input array. If any element in the array is not a number, skip it. If the array is empty, return zero.
 */
 function f(arr) {
-    
+    var sum = 0;
+    for(var i=0; i < arr.length; i++) {
+        if (typeof arr[i] === 'number') {
+            sum += arr[i];
+        } else if (isNaN(i)){ 
+            i+=1;
+        } 
+    }
+    return sum;
 }
 
 function runTest(i) {
diff --git a/problems/problem12.js b/problems/problem12.js
index 2947d1b..64216b0 100644
--- a/problems/problem12.js
+++ b/problems/problem12.js
@@ -2,10 +2,15 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  
+    [[0,1,2,3], [1,3,4,5]],
+    [[],[]],
+    [[1],[1]],
+    [['blue']],
+    [[4,4,5,"a"], [1,4,5]]
 ]
 
 let outputs = [
+  [0,2,4,5], [], [], undefined, ["a", 1]
   
 ]
 
@@ -19,9 +24,44 @@ uniqueElements([0,1,2,3], [1,3,4,5]); // [0,4,5]
 uniqueElements([1,2,3], [1,2,3]); // []
 uniqueElements(2,3); // undefined, not arrays
 */
-function f(arr1, arr2) {
-    
-}
+
+// function f(arr) {
+//     const arr1 = arr[0];
+//     const arr2 = arr[1];
+//     let arr3 = [];
+//     for(let i = 0;i < arr1.length; i++) {
+//         let 
+//     }
+// }
+[[0,1,2,3], [1,3,4,5]]
+
+function f(arr) {
+    var arr1 = arr[0];
+    var arr2 = arr[1];
+    var ret = [];
+    for (var i = 0; i<arr1.length; i++) {
+        var inArray2 = false;
+        var array1Element = arr1[i];
+        for (var j=0;j < arr2.length; j++) {
+            var array2Element = arr2[j];
+            if (array1Element == array2Element) inArray2 = true;
+        }
+        if(!inArray2) {
+            ret.push(arr1[i]);
+        }
+    }
+    return ret;
+
+// function f(arr) {
+//     const arr1 = arr[0];
+//     const arr2 = arr[1];
+//     let newArr = [];
+//     for (let i = 0; i < arr1.length; i++) {
+//         let check = false;
+
+//     }
+//}
+
 
 function runTest(i) {
     if(i > inputs.length) throw new Error("You do not have enough test cases");
@@ -36,3 +76,41 @@ runTest(2);
 runTest(3);
 runTest(4);
 
+
+
+// function memeber (x,lst) {
+//     for (var i =0; i<lst.length;i++) {
+//         if(x == lst[i]) return true;
+//     }
+//     return false
+// }
+
+// function f(arr) {
+//     var arr1 = arr[0];
+//     var arr2 = arr[1];
+//     var ret = [];
+//     for (var i = 0; i<arr1.length; i++) {
+//         if(!member((arr1[i], arr2) && !member(arr1[i], ret)) {
+//             ret.push(arr1[i]);
+//         }
+//     }
+//     return ret;
+// }
+
+// function f(arr) {
+//     var arr1 = arr[0];
+//     var arr2 = arr[1];
+//     var ret = [];
+//     for (var i = 0; i<arr1.length; i++) {
+//         var inArray2 = false;
+//         var array1Element = arr1[i];
+//         for (var j=0;j < arr2.length; j++) {
+//             var array2Element = arr2[j];
+//             if (array1Element == array2Element) inArray2 = true;
+//         }
+//         if(!inArray2) {
+//             ret.push(arr1[i]);
+//         }
+//     }
+//     return ret;
+}
\ No newline at end of file
diff --git a/problems/problem13.js b/problems/problem13.js
index 90669e3..edf6b85 100644
--- a/problems/problem13.js
+++ b/problems/problem13.js
@@ -2,7 +2,7 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  
+  ''
 ]
 
 let outputs = [
diff --git a/problems/problem2.js b/problems/problem2.js
index d54ae74..5a780a2 100644
--- a/problems/problem2.js
+++ b/problems/problem2.js
@@ -2,16 +2,17 @@ var assert = require('assert');
 
 // we need 5 test cases.
 let inputs = [
-
+    "aa", '_as', '1111', 'blue', ""
 ]
 
 let outputs = [
-  
+    'a', 's', '1', 'e', undefined
 ]
 
 // Make this function return the last letter of the string that is passed to it. If the string does not have a last letter, return undefined
 function f(str) {
-    
+    if (str.length == 0) return undefined;
+  return str[str.length-1];
 }
 
 function runTest(i) {
diff --git a/problems/problem3.js b/problems/problem3.js
index 11358c6..10f27de 100644
--- a/problems/problem3.js
+++ b/problems/problem3.js
@@ -3,19 +3,35 @@ var assert = require('assert');
 // we need 7 test cases. I've provided 2.
 let inputs = [
   [2, 4],
-  [-3, 3]
+  [-3, 3],
+  [4, 5],
+  [2, 7],
+  [3, -2],
+  [8, 'p'],
+  [5, undefined]
 ]
 
 let outputs = [
   6,
-  0
+  0,
+  9,
+  9,
+  1,
+  undefined,
+  undefined
 ]
 
+
 /*
 Make this function return the sum of the two numbers that are passed to it. If one of the numbers is not passed, or if anything other than numbers are passed, return undefined.
 */
-function f(x, y) {
-    
+function f(arr) {
+  var x = arr[0]+arr[1];
+  console.log(x);
+  if (isNaN(x) ) {
+    return undefined;
+  }
+  return x;
 }
 
 function runTest(i) {
diff --git a/problems/problem4.js b/problems/problem4.js
index 4082082..7345656 100644
--- a/problems/problem4.js
+++ b/problems/problem4.js
@@ -3,12 +3,24 @@ var assert = require('assert');
 // we need 8 test cases. I've provided the first 2
 let inputs = [
   ["hello", 4],
-  ["", 2]
+  ["", 2],
+  ['blue', 1],
+  ['together', 6],
+  ['azul', 2],
+  ['quesrt', 3],
+  ['strtong', 4],
+  ['red', 2]
 ]
 
 let outputs = [
   "o",
-  undefined
+  undefined,
+  'l',
+  'e',
+  'u',
+  's',
+  'o',
+  'd'
 ]
 
 /*
@@ -20,8 +32,8 @@ f("", 4); // undefined
 f("abc", 0); // a
 
 */
-function f(str, index) {
-    
+function f(x, y) {
+  return x[y];
 }
 
 function runTest(i) {
diff --git a/problems/problem5.js b/problems/problem5.js
index b1e2e44..afde0f5 100644
--- a/problems/problem5.js
+++ b/problems/problem5.js
@@ -2,20 +2,33 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  [2, 7]
+  [2, 7],
+  [3, 1],
+  [6, 2],
+  [4, 'p'],
+  [8, 4]
 ]
 
 let outputs = [
-  14
+  14,
+  3,
+  12,
+  undefined,
+  32
 ]
 
 /*
 Make this function return the product of the two numbers that are passed to it. If one of the numbers is not passed, or if anything other than numbers are passed, return undefined.
 */
-function f(x, y) {
-    
+function f(arr) {
+  var x = arr[0] * arr[1];
+  if (isNaN(x) ) {
+    return undefined;
+  }
+  return x;
 }
 
+
 function runTest(i) {
     if(i > inputs.length) throw new Error("You do not have enough test cases");
     var expected = outputs[i];
diff --git a/problems/problem6.js b/problems/problem6.js
index d31ae17..c1686d4 100644
--- a/problems/problem6.js
+++ b/problems/problem6.js
@@ -4,11 +4,20 @@ var assert = require('assert');
 // we need 6 test cases. 
 let inputs = [
   ["add", 10, 20],
-  ["chair", 20, 10]
+  ["chair", 20, 10],
+  ["mult", 5, 10],
+  ['sub', 10, 5],  //write a different number
+  ['blue', 6, 8],
+  [undefined, 9, 0]
 ]
 
 let outputs = [
-  30
+  30,
+  undefined,
+  50,
+  5,
+  undefined,
+  undefined
 ]
 
 /*
@@ -21,8 +30,17 @@ f("mult", 2, 3); // 6
 f("spoof", 10, 10); // undefined
 
 */
-function f(operation, firstArgument, secondArgument) {
-    
+function f(arr) {
+    var x;
+    if (arr[0] === 'add') {
+      return x = arr[1]+arr[2];
+    } else if (arr[0] === 'mult') {
+      return x = arr[1]*arr[2];
+    } else if (arr[0] === 'sub') {
+      return x = arr[1]-arr[2];
+    } else {
+      return undefined
+    }
 }
 
 function runTest(i) {
diff --git a/problems/problem7.js b/problems/problem7.js
index c3bf4b1..ae27734 100644
--- a/problems/problem7.js
+++ b/problems/problem7.js
@@ -2,11 +2,23 @@ var assert = require('assert');
 
 // we need 7 test cases. 
 let inputs = [
-  
+  ['blue', 2],
+  ['na na na ', 3],
+  ['sa', 8],
+  ['asdasd', 3],
+  ['true', 'bark'],
+  [undefined, 4],
+  ['armor', 0]
 ]
 
 let outputs = [
-  
+  'blueblue',
+  'na na na na na na na na na ',
+  'sasasasasasasasa',
+  'asdasdasdasdasdasd',
+  undefined,
+  undefined,
+  ''
 ]
 
 /*
@@ -19,8 +31,21 @@ f("foo", 3) // "foofoofoo"
 f("fo", 3) // "fofofo"
 f("foo", -1) // undefined
 */
-function f(str, n) {
-    
+function f(str) {
+    var word = str[0];
+    var num = str[1];
+    var empty = '';
+    if (typeof word !== 'string') {
+        return undefined;
+    } else if (isNaN(num)) {
+        return undefined;
+    } else if (num <= 0) {
+        return empty;
+    } else if (num > 0) {
+        return word.repeat(num);
+    } else {
+        return undefined;
+    }
 }
 
 function runTest(i) {
diff --git a/problems/problem8.js b/problems/problem8.js
index 6165932..1b57996 100644
--- a/problems/problem8.js
+++ b/problems/problem8.js
@@ -2,11 +2,19 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  
+  'hello',
+  'blue',
+  'red',
+  'power',
+  'tenacity'
 ]
 
 let outputs = [
-  
+  'olleh',
+  'eulb',
+  'der',
+  'rewop',
+  'yticanet'
 ]
 
 /*
@@ -14,7 +22,11 @@ Make this function return the input string, reversed. For example "hello" would
 You must use a for loop for this exercise.
 */
 function f(str) {
-    
+    var rev = '';
+    for (var i = str.length -1;i >= 0;i--) {
+        rev += str[i] 
+    }
+    return rev;
 }
 
 function runTest(i) {
diff --git a/problems/problem9.js b/problems/problem9.js
index 5c52ef5..9dbab5e 100644
--- a/problems/problem9.js
+++ b/problems/problem9.js
@@ -2,11 +2,19 @@ var assert = require('assert');
 
 // we need 5 test cases. 
 let inputs = [
-  
+  'Welcome to coding',
+  'blue is true',
+  'hello worlds',
+  'beautiful line alignment',
+  ''
 ]
 
 let outputs = [
-  
+  'Welcome',
+  'true',
+  'worlds',
+  'alignment',
+  ''
 ]
 
 /*
@@ -14,7 +22,15 @@ Make this function return the longest word in the input string. If the input str
 If multiple words have the same length, return the last one that matches.
 */
 function f(str) {
-    
+    let words = str.split(" ");
+    let ret = "";
+    for(var i =0; i< words.length;i++){
+      let longest = words[i];
+      if (longest.length >= ret.length) {
+        ret = longest;
+      }
+    }
+    return ret;
 }
 
 function runTest(i) {
diff --git a/problems/test.js b/problems/test.js
new file mode 100644
index 0000000..43a1305
--- /dev/null
+++ b/problems/test.js
@@ -0,0 +1,13 @@
+function m(x) {
+  return x * 2;
+}
+
+function k(f, i, j) {
+  return f(i + 2) + j * 2;
+}
+
+function f(g, h) {
+  return g(h, 1, 4);
+}
+
+console.log(f(k, m));
\ No newline at end of file