You added $\displaystyle{11}\frac{{1}}{{5}}\usepackage{cmbright}\Huge\$ to $\displaystyle-{56}\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ instead of adding $\displaystyle-{11}\frac{{1}}{{5}}\usepackage{cmbright}\Huge\$ to $\displaystyle-{56}\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ . First add $\displaystyle{\left|-{11}\frac{{1}}{{5}}\right|}\usepackage{cmbright}\Huge\$ and $\displaystyle{\left|-{56}\frac{{1}}{{2}}\right|}\usepackage{cmbright}\Huge\$ . Both addends in the problem are negative, so their sum is negative. The correct answer is $\displaystyle-{67}\frac{{7}}{{10}}\usepackage{cmbright}\Huge\$ .