Решите уравнение: a) 5m + 6m = 231; b) 7x - 3x = 412; в) 12x - 2x + 19 = 109.

a) 11m = 231, m = 21. b) 4x = 412, x = 103. в) 10x + 19 = 109, 10x = 90, x = 9.