Solve the system of equations by substitution
-4x + 4y = -40
y = 3x - 4
First, substitute the expression for y from the second equation into the first equation:
-4x + 4(3x - 4) = -40
Simplify the equation:
-4x + 12x - 16 = -40
8x - 16 = -40
8x = -24
x = -3
Now that we have found the value of x, substitute it back into the second equation to find the value of y:
y = 3(-3) - 4
y = -9 - 4
y = -13
Therefore, the solution to the system of equations is x = -3 and y = -13.