Chapter 6 - Section 6.2 - Adding and Subtracting Rational Expressions - Exercise Set - Page 355: 77

$4$

The given expression, $ \left( \dfrac{2x}{3} \right)^2\div\left( \dfrac{x}{3} \right)^2 ,$ simplifies to \begin{array}{l}\require{cancel} \dfrac{4x^2}{9}\div\dfrac{x^2}{9} \\\\= \dfrac{4x^2}{9}\cdot\dfrac{9}{x^2} \\\\= \dfrac{4\cancel{x^2}}{\cancel{9}}\cdot\dfrac{\cancel{9}}{\cancel{x^2}} \\\\= 4 .\end{array}