How do you rationalize (4sqrt6)/(sqrt30)?

First note that $\sqrt{30} = \sqrt{5 \cdot 6} = \sqrt{5} \cdot \sqrt{6}$
So $\frac{4 \sqrt{6}}{\sqrt{30}} = \frac{4 \sqrt{6}}{\sqrt{5} \sqrt{6}} = \frac{4}{\sqrt{5}}$
Then rationalize the denominator by multiplying both numerator and denominator by $\sqrt{5}$
$\frac{4}{\sqrt{5}} = \frac{4 \sqrt{5}}{\sqrt{5} \sqrt{5}} = \frac{4 \sqrt{5}}{5}$