3 1/3 - 2 2/5 + ?

First, find the common denominator. Both 3 and 5 go into 15. Then change these fractions into equivalent fractions with the same denominator.

3 1/3 = 3 5/15
2 2/5 = 2 6/15

3 5/15 - 2 6/15 = 50/15 - 36/15 = 14/15