#### Answer

The answer is $=-3(\sqrt 3+\sqrt 5)$.

#### Work Step by Step

The given expression is
$\frac{6}{\sqrt 3-\sqrt 5}$
Divide and multiply by $\sqrt 3+\sqrt 5$ to rationalize the denominator.
$=\frac{6}{\sqrt 3-\sqrt 5}\cdot \frac{\sqrt 3+\sqrt 5}{\sqrt 3+\sqrt 5}$
$=\frac{6(\sqrt 3+\sqrt 5)}{3-5}$
$=\frac{6(\sqrt 3+\sqrt 5)}{-2}$
$=-3(\sqrt 3+\sqrt 5)$.