15. x-5(x + 4) = 2(x – 8) +8.

$$\begin{aligned}&x - 5(x + 4) = 2(x - 8) + 8\\ &x - 5x - 20 = 2x - 16 + 8\\ &-4x - 20 = 2x - 8\\ &-4x - 2x = -8 + 20\\ &-6x = 12\\ &x = \frac{12}{-6}\\ &x = -2\end{aligned}$$ Ответ: $$\boxed{x = -2}$$