Решим уравнение:
$$6x - 8 = 5x - 3(x - 4)$$$$6x - 8 = 5x - 3x + 12$$$$6x - 8 = 2x + 12$$$$6x - 2x = 12 + 8$$$$4x = 20$$$$x = 5$$
Ответ: 5