This exercise teaches of how fruitful functions work as well as creating a loop.To extend on what have learn previously about functions and to understand the way loop works.

y=4
x=15
x+y
x-y
x/y
x*y
x%y
y = x-1
def factorial(x):
if x==0:
return 1
else:
recurse = factorial (x-1)
result = x * recurse
return result