Fraction. please show work

Question

Before recess jerry put together 2/5 of his puzzle. after recess he put together another1/3 of the puzzle. How much of the puzzle was completed

Answer 1

1 - 2/5 - 1/3 = the remaining puzzle to be completed

15/15 - 6/15 - 5/15 = (15-6-5)/15 = 4/15 left

convert each of the 3 terms to the same denominator

1 = 15/15

2/5 = 6/15

1/3 = 5/15

then combine the numerators over the denominator of 15