Can’t see what you’re talking about
i need more info. Is this the whole question?
If you reduce them by 12 you'll get

If that's what you're asking
-4 first we rearrange the question x-2y=8
x-2y=8
-2y=-x+8
y=1/2x-4 (divide by -2 everywhere)
-4 is the y intercept.