X^a/b is
![\sqrt[b]{x^a}](https://tex.z-dn.net/?f=%20%5Csqrt%5Bb%5D%7Bx%5Ea%7D%20)
. The way I memorise that is x^1/3 is the cubic root of x. Do you get it? In that case, x is raised to a power of 1 and the cubic root is practically has a power of 3.
In your example,
![\sqrt[ \frac{3}{2} ]{16 x^4}](https://tex.z-dn.net/?f=%20%5Csqrt%5B%20%5Cfrac%7B3%7D%7B2%7D%20%5D%7B16%20x%5E4%7D)
is practically square rooting each term then cubing them individually. Remember when square-rooting any index you halve it. I'll elaborate:

=


= 4
Then cube each,

= 64
and

=

As for the 2nd part: you must use the rules of indices.

So breaking the question up:
3 * 3 = 9

stays as is since the 2nd term does not contain x
now:

This makes your final answer look like this:

I hope that helped and good luck in your test!