4) 2(4x + 5) - 3(x + 6) = 9x + 8;

Решение:

1. \( 2(4x + 5) - 3(x + 6) = 9x + 8 \)
2. \( 8x + 10 - 3x - 18 = 9x + 8 \)
3. \( 5x - 8 = 9x + 8 \)
4. \( 5x - 9x = 8 + 8 \)
5. \( -4x = 16 \)
6. \( x = \frac{16}{-4} \)
7. \( x = -4 \)

Ответ: x = -4.