Solve the following system of equations by substitution and select the correct answer below:
2x − 4y = 24
4x − 12y = 36
x = 18, y = 3
x = 18, y = −3
x = −18, y = 3
x = −18, y = −3
2x − 4y = 24
4x − 12y = 36
x = 18, y = 3
x = 18, y = −3
x = −18, y = 3
x = −18, y = −3