Correct. To simplify the expression, find the cube root of 216 and the cube root of $\displaystyle{{b}}^{{3}}\usepackage{cmbright}\Huge\$ .

$\displaystyle{\sqrt[{{3}}]{{{216}{{b}}^{{3}}}}}={\sqrt[{{3}}]{{{6}\cdot{6}\cdot{6}\cdot{{b}}^{{3}}}}}={\sqrt[{{3}}]{{{{6}}^{{3}}\cdot{{b}}^{{3}}}}}={\sqrt[{{3}}]{{{{6}}^{{3}}}}}\cdot{\sqrt[{{3}}]{{{{b}}^{{3}}}}}={6}{b}\usepackage{cmbright}\Huge\$