Chapter 9 - Roots and Radicals - 9.1 - Roots and Radicals - Problem Set 9.1 - Page 401: 76

$\approx-8.7$

Using the properties of radicals, a rational approximation (to the nearest tenth) of the given expression, $ 7\sqrt{3}-12\sqrt{3} ,$ is \begin{array}{l}\require{cancel} (7-12)\sqrt{3} \\\\= -5\sqrt{3} \\\\ \approx-8.7 .\end{array}