Each side has own formula, so which side is X
For this problem, you would have to use a system of equations. Hope this helps!
Y = -x + 4.....so sub in -x + 4 in for y in the other equation
x + 2y = -8
x + 2(-x + 4) = -8
x - 2x + 8 = -8
x - 2x = -8 - 8
-x = -16
x = 16
y = -x + 4
y = -16 + 4
y = - 12
one solution (16,-12)
y/x = k
6.4/4 = 1.6
11.2 / 7 =1.6
16/10 = 1.6
20.8 /13 =1.6
This is a direct variation and the constant is 1.6
y=1.6x