Chapter 5 - Exponents and Polynomials - 5.6 - Integral Exponents and Scientific Notation - Problem Set 5.6 - Page 224: 76

$\dfrac{1}{a^{9}b^{6}}$

Using the laws of exponents, the given expression, $ \left( \dfrac{a^{3}}{b^{-2}} \right)^{-3} ,$ is equivalent to \begin{array}{l}\require{cancel} \dfrac{a^{3(-3)}}{b^{-2(-3)}} \\\\= \dfrac{a^{-9}}{b^{6}} \\\\= \dfrac{1}{a^{9}b^{6}} .\end{array}