Chapter 7 - Section 7.5 - Rationalizing Denominators and Numerators of Radical Expressions - Exercise Set - Page 445: 23

$\dfrac{\sqrt{6x}}{10}$

Rationalizing the denominator of $ \sqrt[]{\dfrac{3x}{50}} $ results to \begin{array}{l} \sqrt[]{\dfrac{3x}{50}} \cdot \sqrt[]{\dfrac{2}{2}} \\\\= \sqrt[]{\dfrac{6x}{100}} \\\\= \dfrac{\sqrt{6x}}{10} .\end{array}