diff --git a/mandatory/1-syntax-errors.js b/mandatory/1-syntax-errors.js
index a10cc9ac2..8864f4f9f 100644
--- a/mandatory/1-syntax-errors.js
+++ b/mandatory/1-syntax-errors.js
@@ -1,16 +1,16 @@
 // 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;
 }
 
 /* 
@@ -27,7 +27,7 @@ To run the tests for just this one file, type `npm test -- --testPathPattern 1-s
 
 test("addNumbers adds numbers correctly", () => {
   expect(addNumbers(3, 4, 6)).toEqual(13);
-});
+}); 
 
 test("introduceMe function returns the correct string", () => {
   expect(introduceMe("Sonjide", 27)).toEqual(
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..8f78be9a2 100644
--- a/mandatory/3-function-output.js
+++ b/mandatory/3-function-output.js
@@ -9,6 +9,7 @@ function combine2Words(word1, word2) {
 }
 
 function concatenate(firstWord, secondWord, thirdWord) {
+  return 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.
 }
diff --git a/mandatory/4-tax.js b/mandatory/4-tax.js
index ba77c7ae2..dad8f9bea 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(price) {
+  return price + (price * (20 / 100 ))
+}
 
 /*
   CURRENCY FORMATTING
@@ -17,7 +19,11 @@ function calculateSalesTax() {}
   Remember that the prices must include the sales tax (hint: you already wrote a function for this!)
 */
 
-function addTaxAndFormatCurrency() {}
+function addTaxAndFormatCurrency(price) {
+  tax = calculateSalesTax(price);//calculating tax
+  //final_price = price + tax; //calculating final price
+ return `£${tax.toFixed(2)}`; 
+}
 
 /* 
 ===================================================
diff --git a/mandatory/test.js b/mandatory/test.js
new file mode 100644
index 000000000..1e23901e4
--- /dev/null
+++ b/mandatory/test.js
@@ -0,0 +1,6 @@
+function calculateSalesTax(price) {
+  return price + (price * (20 / 100 ))
+}
+//console.log(calculateSalesTax(10));
+tax = calculateSalesTax(100)
+console.log(tax)
\ No newline at end of file