Answer
$3\sqrt{3}$
Work Step by Step
Factor each radicand so that one of the factors is a perfect square to obtain:
$=3\sqrt{4(3)} - \sqrt{9(3)}
\\=3\sqrt{2^2(3)} - \sqrt{3^2(3)}$
Simplify each radical to obtain:
$=3\cdot 2\sqrt{3} - 3\sqrt{3}
\\=6\sqrt{3} - 3\sqrt{3}$
Factor out $\sqrt{3}$ to obtain:
$=\sqrt{3}(6-3)
\\=\sqrt{3} \cdot 3
\\=3\sqrt{3}$
