Incorrect. A binomial in the form $\displaystyle{{a}}^{{3}}-{{b}}^{{3}}\usepackage{cmbright}\Huge\$ can be factored as $\displaystyle{\left({a}-{b}\right)}{\left({{a}}^{{2}}+{a}{b}+{{b}}^{{2}}\right)}\usepackage{cmbright}\Huge\$ . $\displaystyle{125}{{m}}^{{3}}={{\left({5}{m}\right)}}^{{3}}\usepackage{cmbright}\Huge\$ and $\displaystyle{8}{{n}}^{{3}}={{\left({2}{n}\right)}}^{{3}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{a}={5}{m}\usepackage{cmbright}\Huge\$ and $\displaystyle{b}={2}{n}\usepackage{cmbright}\Huge\$ . The correct answer is 10.