Answer:
[tex] {2}^{(5x + 3)} = \frac{1}{128} \\ {2}^{(5x + 3)} = \frac{1}{ {2}^{7} } \\ {2}^{(5x + 3)} = {2}^{ (- 7)} \\ 5x + 3 = - 7 \\ 5x = - 7 - 3 \\ 5x = - 10 \\ x = \frac{ - 10}{5} \\ \boxed{x = - 2}[/tex]