Chapter 5 - Exponents and Polynomials - 5.6 - Integral Exponents and Scientific Notation - Problem Set 5.6 - Page 224: 72

$\dfrac{y^6}{9x^4}$

Using the laws of exponents, the given expression, $ (3x^2y^{-3})^{-2} ,$ is equivalent to \begin{array}{l}\require{cancel} 3^{-2}x^{2(-2)}y^{-3(-2)} \\\\= 3^{-2}x^{-4}y^{6} \\\\= \dfrac{y^6}{3^2x^4} \\\\= \dfrac{y^6}{9x^4} .\end{array}