Question

The value of y varies directly with x, and y = 4 when x = 1.Find y when x = −3.

Answer 1

First you need to find k.

k = y/x

k = 4/1
k = 4

y = kx
y = 4(-3)
y = -12

Answer 2

Take a look at http://www.regentsprep.org/Regents/math/ALGEBRA/AO4/Ldirect.htm
for more information on direct variation..