diff --git a/exercises/E-strings-concatenation/exercise.js b/exercises/E-strings-concatenation/exercise.js
index 2cffa6a81..2221c2dba 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`
+let greetingStart = "Hello my name is ";  
+let firstName = "Rabie ";
 
-console.log(message);
+console.log(greetingStart + firstName);
diff --git a/exercises/F-strings-methods/exercise.js b/exercises/F-strings-methods/exercise.js
index 2cffa6a81..d4bb67235 100644
--- a/exercises/F-strings-methods/exercise.js
+++ b/exercises/F-strings-methods/exercise.js
@@ -1,3 +1,11 @@
-// Start by creating a variable `message`
+let firstMessage = "Hello my name is "; 
+let secondmessage = "and my name is "; 
+let thirdmessage = " long"; 
+let name = "Rabie "; 
+let length = name.length; 
+
+
+let message = firstMessage + name + secondmessage + length + thirdmessage;
+
 
 console.log(message);
diff --git a/exercises/F-strings-methods/exercise2.js b/exercises/F-strings-methods/exercise2.js
index b4b46943d..d4bb67235 100644
--- a/exercises/F-strings-methods/exercise2.js
+++ b/exercises/F-strings-methods/exercise2.js
@@ -1,3 +1,11 @@
-const name = " Daniel  ";
+let firstMessage = "Hello my name is "; 
+let secondmessage = "and my name is "; 
+let thirdmessage = " long"; 
+let name = "Rabie "; 
+let length = name.length; 
+
+
+let message = firstMessage + name + secondmessage + length + thirdmessage;
+
 
 console.log(message);
diff --git a/exercises/G-numbers/exercise.js b/exercises/G-numbers/exercise.js
index 49e7bc00b..129797002 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 numOfStudents = 15; 
+let numOfmentores = 8; 
+let total = numOfStudents + numOfmentores; 
+
+console.log("Number of student: " + numOfStudents); 
+console.log("Number of mentores: " + numOfmentores); 
+console.log("Total number of students and mentores " + total); 
diff --git a/exercises/I-floats/exercise.js b/exercises/I-floats/exercise.js
index a5bbcd852..9af54fea6 100644
--- a/exercises/I-floats/exercise.js
+++ b/exercises/I-floats/exercise.js
@@ -1,2 +1,9 @@
-var numberOfStudents = 15;
-var numberOfMentors = 8;
+let numOfStudents = 15; 
+let numOfmentores = 8; 
+let total = numOfStudents + numOfmentores; 
+
+let percentageOfStudents = (numOfStudents / total) * 100; 
+let percentageOfMentores = (numOfmentores / total) * 100; 
+
+console.log("Percentage Students: " + Math.round(percentageOfStudents) + "%");
+console.log("Percentage Mentores: " + Math.round (percentageOfMentores) + "%");
diff --git a/exercises/J-functions/exercise.js b/exercises/J-functions/exercise.js
index 0ae5850e5..d5b9b5740 100644
--- a/exercises/J-functions/exercise.js
+++ b/exercises/J-functions/exercise.js
@@ -1,7 +1,8 @@
 function halve(number) {
-  // complete the function here
+  return number/2; 
 }
 
 var result = halve(12);
 
 console.log(result);
+
diff --git a/exercises/J-functions/exercise2.js b/exercises/J-functions/exercise2.js
index 82ef5e780..ca499a8ab 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..9ccf2952a 100644
--- a/exercises/K-functions-parameters/exercise.js
+++ b/exercises/K-functions-parameters/exercise.js
@@ -1,9 +1,7 @@
-// Complete the function so that it takes input parameters
-function multiply() {
-  // Calculate the result of the function and return it
+function multiply(a, b){
+    return a * b; 
 }
 
-// Assign the result of calling the function the variable `result`
-var result = multiply(3, 4);
+let result = multiply(5, 3); 
 
 console.log(result);
diff --git a/exercises/K-functions-parameters/exercise2.js b/exercises/K-functions-parameters/exercise2.js
index db7a8904b..5d3d39c6f 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(a, b){
+    return a / b; 
+}
 
-var result = divide(3, 4);
+let result = divide(9, 3); 
 
 console.log(result);
diff --git a/exercises/K-functions-parameters/exercise3.js b/exercises/K-functions-parameters/exercise3.js
index 537e9f4ec..f8cbe7fc1 100644
--- a/exercises/K-functions-parameters/exercise3.js
+++ b/exercises/K-functions-parameters/exercise3.js
@@ -1,5 +1,8 @@
-// Write your function here
+function createGreeting (name){
+    console.log("Hello, my name is " + name); 
+    return name;
+}
 
-var greeting = createGreeting("Daniel");
+let greeting = createGreeting("Rabie"); 
 
 console.log(greeting);
diff --git a/exercises/K-functions-parameters/exercise4.js b/exercises/K-functions-parameters/exercise4.js
index 7ab44589e..48f3144ea 100644
--- a/exercises/K-functions-parameters/exercise4.js
+++ b/exercises/K-functions-parameters/exercise4.js
@@ -1,5 +1,8 @@
-// Declare your function first
+function summation(num1, num2){
+    let sum = num1 + num2; 
+    return sum 
+}
 
-// Call the function and assign to a variable `sum`
+let result = summation(13, 124); 
 
-console.log(sum);
+console.log(result);
diff --git a/exercises/K-functions-parameters/exercise5.js b/exercises/K-functions-parameters/exercise5.js
index 7c5bcd605..7a6a5f48e 100644
--- a/exercises/K-functions-parameters/exercise5.js
+++ b/exercises/K-functions-parameters/exercise5.js
@@ -1,5 +1,7 @@
-// Declare your function here
+function greeting(name, age){
+    let message = "Hello, my name is " + name + " and I am " + age + " years old"; 
+    return message;
+}
 
-const greeting = createLongGreeting("Daniel", 30);
-
-console.log(greeting);
+let greetingMessage = greeting("Rabie", 27);
+console.log(greetingMessage); 
diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..bd5b0e3f2 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,18 +1,19 @@
 // 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) { //There are missing "," between each argument. 
   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"; // after name there needs to be + also after the string. 
+}
 function getTotal(a, b) {
-  total = a ++ b;
+  let total = a + b; 
 
-  return "The total is total";
+  return "The total is " + total; 
 }
 
+
 /* 
 ===================================================
 ======= TESTS - DO NOT MODIFY BELOW THIS LINE =====
diff --git a/mandatory/2-logic-error.js b/mandatory/2-logic-error.js
index 9cca7603b..82e864c5d 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(); // wordtrim is undefined word. 
 }
 
 function getStringLength(word) {
-  return "word".length();
+  return word.length; // word shouldn't be a string. 
 }
 
 function multiply(a, b, c) {
-  a * b * c;
-  return;
+  
+  return a * b * c; // the return should have the multiplication like: return a * b * c; 
 }
 
 /* 
diff --git a/mandatory/3-function-output.js b/mandatory/3-function-output.js
index 5a953ba60..299307741 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -11,6 +11,7 @@ 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 + " " + secondWord + " " + thirdWord; 
 }
 
 /* 
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..d488aa012 100644
--- a/mandatory/4-tax.js
+++ b/mandatory/4-tax.js
@@ -5,7 +5,9 @@
   Sales tax is 20% of the price of the product.
 */
 
-function calculateSalesTax() {}
+function calculateSalesTax(priceBeforeTax) {
+  return priceBeforeTax + (priceBeforeTax * 0.2); 
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,10 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(priceBeforeTax) {
+  let priceAfterTax = calculateSalesTax(priceBeforeTax);
+  return `£${priceAfterTax.toFixed(2)}`; 
+}
 
 /* 
 ===================================================