2y + 2x = 8
2y - 4x = 2
solve both for 2y
2y + 2x = 8
2y = 8 - 2x
second
2y - 4x = 2
2y = 4x + 2
they are both equal to 2y, so you can set them equal to each other
4x + 2 = 8 - 2x
4x = 6 - 2x
6x = 6
x = 1
2y -4(1) = 2
2y - 4 = 2
2y = 6
y = 3
check
2(3) + 2(1) = 8
6 + 2 = 8
true