Done

index.js

@@ -0,0 +1,35 @@
+ function makeInt(n){
+   return parseInt(n,10)
+ }
+
+ function preserveDecimal(n){
+   return parseFloat(n)
+ }
+
+ function add(a,b){
+   return a + b
+ }
+
+ function substract(a, b){
+   return a - b
+ }
+ function multiply(a,b){
+   return a * b
+ }
+
+ function divide(a , b){
+   if (b !==0 ){
+     return a/b
+   }
+   else {
+     return NaN
+   }
+ }
+
+ function inc(n){
+   return ++n
+ }
+
+ function dec(n){
+   return --n
+ }

test/index-test.js

@@ -10,7 +10,7 @@ it('add(a, b) adds two numbers and returns the result', function() {
 })
 
 it('subtract(a, b) subtracts b from a and returns the result', function() {
-  expect(subtract(a, b)).toEqual(a - b)
+  expect(substract(a, b)).toEqual(a - b)
 })
 
 it('multiply(a, b) multiplies two numbers and returns the result', function() {