Chapter 5 - Section 5.2 - More Work with Exponents and Scientific Notation - Exercise Set - Page 268: 54

$\dfrac{b^{7}}{7a^{5}}$

Using laws of exponents, the given expression simplifies to \begin{align*} & \dfrac{7^{-1}a^{-3}b^{5}}{a^{2}b^{-2}} \\\\&= \dfrac{a^{-3-2}b^{5-(-2)}}{7} \\\\&= \dfrac{a^{-5}b^{7}}{7} \\\\&= \dfrac{b^{7}}{7a^{5}} .\end{align*}