We need to rationalize the denominator by removing radicals (the root) from it.

So, to get rid of:

in the denominator, we need to multiply by:

above and bellow the fraction bar, and that is why we have:

27 = 3^3

Keep in mind that you can obtain an explanation for any step by clicking on it.

Please note that you cannot click on the very first expression, which is the original problem.