Writing a direct variation equation

Question

Suppose that y varies directly with x , and y = 10 when x = -5.

A) Write a direct variation equation that relates x and y.

B) Find y when x = 4.

y =

Answer 1

Since varies directly; y = kx given y= 10 & x= -5 then 10 = k(-5) so k = -2

then can solve when x = 4 ; y = -2(5) = -10