You may have tried to simplify $\displaystyle\frac{{{h}}^{{3}}}{{{h}}^{{1}}}\usepackage{cmbright}\Huge\$ , when you should have been simplifying $\displaystyle\frac{{{h}}^{{\frac{{2}}{{3}}}}}{{{h}}^{{\frac{{1}}{{2}}}}}\usepackage{cmbright}\Huge\$ instead.