Question

y varies directly as x, and y=7 when x=4, find y when x=12

Answer 1

Since y varies with x, the same we do to y, applies to x. 

x = 4  y=7

x= 4*3 = 12
x= 7*3 = 21

Therefore, x = 21

Final answer:  x=21    and   y= 12

Answer 2

♥ Lets gather the information we know:
$x = 4 y=7$
♥ Now lets multiply and solve:
if x= 4*3 and 4*3 is 12
if x= 7*3 and 7*3 is  21
♥ And since 7*3=21, our answer is 21