Given that y varies directly with x and that y = 60 when x = 20, find y when x = 12.

1. y varies directly with x

2. substitute the value of x and y in the equation below

y=kx

where k is the constant term

60=20k

k=60/20

k=30

:y=30x ... is the law

To find y when x is 12

You reinstate the law which is y=30x

Then substitutes the value of x to determine y

y=30*12

y=36.