You may have been thinking about division of fractions. You may have multiplied the exponent $\displaystyle\frac{{2}}{{3}}\usepackage{cmbright}\Huge\$ by $\displaystyle\frac{{3}}{{1}}\usepackage{cmbright}\Huge\$ to get $\displaystyle{{w}}^{{2}}\usepackage{cmbright}\Huge\$ , but you should have used the rule: $\displaystyle\frac{{{{x}}^{{a}}}}{{{{x}}^{{b}}}}={{x}}^{{{a}-{b}}}\usepackage{cmbright}\Huge\$