Answer:
x = -2, y = 7
Step-by-step explanation:
Since it's a system of equations, we know that the they use the same variables. To use substitution to solve a system of equation, we must take one equation and solve it for a variable, then you plug the solution into that variable for the other equation:
-2x + y = 11
y = 2x + 11
-------
4x + 4y = 20
4x + 4(2x + 11) = 20
4x + 8x + 44 = 20
12x + 44 = 20
12x = -24
x = -2
Then we can plug "x" into the first equation:
-2x + y = 11
-2(-2) + y = 11
4 + y = 11
y = 7
