Solve the simultaneous equations 2x + y = 18 and x - y = 6

2x + y = 6x - y = 6x = 6 + y => 2(6 + y) + y = 18 => 12 + 3y = 18 => 3y = 6 => y = 2x - (2) = 6 => x = 8x = 8, y = 2