Answer:
-18
First, let's use the first equation, y = -2x, and substitute it into the second equation. We substitute y with -2x in the second equation:
-2x = -6x + 36
Now, we can solve for x:
Add 6x to both sides:
4x = 36
Divide by 4:
x = 9
Now that we have the value of x, we can substitute it back into the first equation y = -2x to solve for y:
y = -2(9)
y = -18
So, the solution to the system by substitution is x = 9 and y = -18.
