Answer
(a) $6\sqrt[3]{2}$
(b) $\frac{\sqrt{2}}{3}$
(c) $\frac{3\sqrt{3}}{2}$
Work Step by Step
(a) 3 $\sqrt[3]{16}=3\sqrt[3]{2*2^{3}}=3*2\sqrt[3]{2}=6\sqrt[3]{2}$
(b) $\frac{\sqrt{18}}{\sqrt{81}}=\sqrt{\frac{18}{81}}=\sqrt{\frac{2}{9}}=\frac{\sqrt{2}}{\sqrt{9}}=\frac{\sqrt{2}}{3}$
(c) $\sqrt{\frac{27}{4}}=\sqrt{\frac{3*3^{2}}{2^{2}}}=\frac{3\sqrt{3}}{2}$