Use the rule $\displaystyle\frac{{{{x}}^{{a}}}}{{{{x}}^{{b}}}}={{x}}^{{{a}-{b}}}\usepackage{cmbright}\Huge\$ : $\displaystyle\frac{{{{w}}^{{\frac{{2}}{{3}}}}}}{{{{w}}^{{\frac{{1}}{{3}}}}}}={{w}}^{{\frac{{2}}{{3}}-\frac{{1}}{{3}}}}={{w}}^{{\frac{{1}}{{3}}}}\usepackage{cmbright}\Huge\$

Change to radical form: $\displaystyle{{w}}^{{\frac{{1}}{{3}}}}={\sqrt[{{3}}]{{{w}}}}\usepackage{cmbright}\Huge\$