You may have incorrectly simplified the numerator by ignoring the absolute value symbols, finding $\displaystyle{8}-{7}+{\left(-{11}\right)}\usepackage{cmbright}\Huge\$ and obtaining $\displaystyle-{10}\usepackage{cmbright}\Huge\$ . The absolute value must be simplified first. The correct answer is $\displaystyle\frac{{1}}{{2}}\usepackage{cmbright}\Huge\$ .