Not sure if you were having trouble with this but just wanted to point out a couple of things I noticed.
On your if statements, if you're comparing the values of two items, you need the equality operator ==, not the assignment operator =.
With the division, you might want to check the value entered for b to make sure you don't end up dividing by zero and crashing.
Dividing two integers will also give you an integer division result - if someone enters 5 for a and 3 for b, they might not expect to get 1. You'll need to tweak the code a little bit if you want them to get a floating point result.