Chapter 5 - Section 5.2 - More Work with Exponents and Scientific Notation - Exercise Set - Page 268: 42

$\dfrac{y^{16}}{64x^5}$

Using laws of exponents, the given expression simplifies to \begin{align*} & \dfrac{8^{-2}x^{-3}y^{11}}{x^{2}y^{-5}} \\\\&= 8^{-2}x^{-3-2}y^{11-(-5)} \\&= 8^{-2}x^{-5}y^{16} \\\\&= \dfrac{y^{16}}{8^2x^5} \\\\&= \dfrac{y^{16}}{64x^5} .\end{align*}