You may have subtracted 24 from 72 and subtracted the exponents, obtaining $\displaystyle{48}{x}\usepackage{cmbright}\Huge\$ under the radical, which you then simplified. Rewrite using $\displaystyle\frac{\sqrt{{a}}}{\sqrt{{b}}}=\sqrt{{\frac{{a}}{{b}}}}\usepackage{cmbright}\Huge\$ and simplify by identifying similar factors in the numerator and denominator.