To solve for y, we need to isolate y on one side of the equation.

Starting with the given equation:
Х - 10 = 4у - 40

First, let's add 10 to both sides of the equation to get rid of the -10 on the left side:
Х = 4у - 30

Next, let's isolate the y term by dividing both sides of the equation by 4:
(Х + 30)/4 = y
y = (Х + 30)/4

Therefore, the solution for y in terms of x is y = (Х + 30)/4.