#### Answer

$\frac{x-25}{-3\sqrt x+15}$

#### Work Step by Step

$\frac{\sqrt x+5}{-3}\times\frac{\sqrt x-5}{\sqrt x-5}$
=$\frac{(\sqrt x+5)(\sqrt x-5)}{-3(\sqrt x-5)}$
=$\frac{\sqrt x(\sqrt x-5)+5(\sqrt x-5)}{-3\sqrt x+15}$
=$\frac{x-5\sqrt x+5\sqrt x-25}{-3\sqrt x+15}$
=$\frac{x-25}{-3\sqrt x+15}$