You may have simplified the numerator to $\displaystyle-{\left|-{6}\right|}\usepackage{cmbright}\Huge\$ and then thought that the negatives would cancel, which would happen if you had $\displaystyle-{\left(-{6}\right)}\usepackage{cmbright}\Huge\$ . Here, however, $\displaystyle{\left|-{6}\right|}={6}\usepackage{cmbright}\Huge\$ , so with another negative sign in front, you end up with $\displaystyle-{6}\usepackage{cmbright}\Huge\$ .