Suppose y varies directly with x, and y=8 when x=-4. Find x when y=10

Answer 1

Using formula

y = kx

8 = k(-4)

-2 = k

10 = -2x

-5 = x

Using proportion

-4 : 8 :: x : 10

8x = (-4)(10)

8x = -40

x = -5