Question

Two fifths of the instruments in the marching band are brass, one third are percussion, and the rest are woodwinds. What fraction of the band is woodwinds? Help me

Answer 1

First calculate how much of the whole band the brass and percussion take. 
2/5+1/3= 6/15+5/15= 11/15
A whole is 1, which is 15/15, so 
15/15-11/15=4/15 
4/15 of the band is woodwinds.

Answer 2

2/5 of instruments= brass
1/3 of instruments= percussion
so add 2/5 and 1/3=  6/15+5/15= 11/15

So 15/15-11/15= 4/15
So Woodwinds make up 4/15 of the band