Question

If y varies directly as x, and y = 12 when x = 15, find x when y = 21.

Answer 1

y=kx where k is a constant
sub y=12, x=15
12=15k
k=12/15
hence, y=(12/15)x
sub y=21,
(12/15)x=21
x=21÷12/15=26.25

should be right..