Solve each system by substitution

y=-3x
4x - 2y = -20

Substitute y = -3x into the second equation:

4x - 2(-3x) = -20
4x + 6x = -20
10x = -20
x = -2

Now substitute x = -2 back into the first equation to find y:

y = -3(-2)
y = 6

Therefore, the solution to the system is x = -2 and y = 6.