You found $\displaystyle{3}\sqrt{{{729}{{s}}^{{9}}}}\usepackage{cmbright}\Huge\$ instead of $\displaystyle{\sqrt[{{3}}]{{{729}{{s}}^{{9}}}}}\usepackage{cmbright}\Huge\$ . Factor 729 into three equal numbers. Next, factor and rewrite $\displaystyle{{s}}^{{9}}\usepackage{cmbright}\Huge\$ with an exponent of 3. Find the cube root of each of these and multiply. The correct answer is $\displaystyle{9}{{s}}^{{3}}\usepackage{cmbright}\Huge\$ .