if they vary directly, u can make a proportion
-7/3 = x/-5.....-7 to 3 = x to -5
cross multiply
(3)(x) = (-7)(-5)
3x = 35
x = 35/3
x = 11 2/3
check..
-7/3 = (35/3) / -5
cross multiply
3(35/3) = (-5)(-7)
35 = 35 (correct)
so when y = -5, x = 35/3 or 11 2/3