Answer:
x = 77 - 2y
y = -x/2 + 77/2
Explanation:
2x + 4y - 31 = 123
add 31 both sides
2x + 4y - 31 + 31 = 123 + 31
2x +4y = 154
Solve for x
2x = 154 - 4y
divide both sides by 2
x = 77 - 2y
solve for y
2y = 77 - x
divide both sides by 2
y = 77/2 - x/2