Chapter 10 - Exponents and Radicals - 10.4 Dividing Radical Expressions - 10.4 Exercise Set - Page 653: 45

$\dfrac{2\sqrt{15}}{21}$

Rationalizing the denominator of the given expression, $ \dfrac{2\sqrt{5}}{7\sqrt{3}} ,$ we find: \begin{array}{l}\require{cancel} \dfrac{2\sqrt{5}}{7\sqrt{3}}\cdot\dfrac{\sqrt{3}}{\sqrt{3}} \\\\= \dfrac{2\sqrt{15}}{7\sqrt{(3)^2}} \\\\= \dfrac{2\sqrt{15}}{7\cdot3} \\\\= \dfrac{2\sqrt{15}}{21} .\end{array}