Решим уравнение:
$$5 + 2x = 3(2x - 5) - 8$$$$5 + 2x = 6x - 15 - 8$$$$5 + 2x = 6x - 23$$$$2x - 6x = -23 - 5$$$$-4x = -28$$$$x = 7$$
Ответ: 7