1) 2 * (x - y) - a * (x - y) = (2 - a) * (x - y)
2) 7 * (x + y) - a * (x + y) = (7 - a) * (x + y)
3) 2 * (a - b) + c * (b - a) = 2 * (a - b) - c * (a - b) = (2 - c) * (a - b)
4) 2a * (b - 3) - 5c * (3 - b) = 2a * (b - 3) + 5c * (b - 3) = (2a + 5c) * (b - 3)