Chapter 5 - Section 5.7 - Negative Exponents and Scientific Notation - Exercise Set - Page 408: 43

$\dfrac{7}{5w^{8}}$

Using the laws of exponents, the given expression, $ \dfrac{7w^5}{5w^{13}} ,$ simplifies to \begin{array}{l}\require{cancel} \dfrac{7w^{5-13}}{5} \\\\= \dfrac{7w^{-8}}{5} \\\\= \dfrac{7}{5w^{8}} .\end{array}