Hi,

I assume you are to simplify this expression. I can help get you started. When you see an expression with a root in the denominator such as $\large \frac{15}{\sqrt5},$ you can try this

\[\frac{15}{\sqrt5} = \frac{15 \sqrt 5}{\sqrt 5 \sqrt 5} = \frac{15 \sqrt{5}} {5} = 3 \sqrt{5}.\]

I hope this helps,
Penny