4x + y = 12
Get y by itself
Subtract 4x
y = -4x + 12
Since you know what y is, you can plug the value into the second equation
6x + 2(-4x + 12) = 18
6x - 8x + 24 = 18
-2x = -6
x = 3
Plug the value 3 into x for y = -4x + 12 in order to find y
-4(3) + 12 = y, y = 0
Solution: x = 3, y = 0
