You may have divided $\displaystyle{38}\div{19}\usepackage{cmbright}\Huge\$ and set it over the denominator 4. You need to find $\displaystyle{4}\frac{{3}}{{4}}\div{38}=\frac{{19}}{{4}}\cdot\frac{{1}}{{38}}\usepackage{cmbright}\Huge\$ to get the answer.