Question

It's a classroom contact 35 students 2 by 5 of which are girls then how many boys in the class

Answer 1

HOPE THIS HELPS MATE

2/5 * 35 = 14 (No. of girls)  (Let this be x)

No. of boys =  35-x = 35-14=21

Answer 2

$35 \times 2 \div 5 = 14 \\ 35 \times 3 \div 5 = 21$
Their ratio is 3:2 there are 21 boys in the class