You probably found $\displaystyle-{63}+{25}\usepackage{cmbright}\Huge\$ incorrectly by adding 63 and 25 and then putting a negative sign in front. Instead, you should subtract $\displaystyle{63}-{25}\usepackage{cmbright}\Huge\$ and then make the result negative. The correct answer is $\displaystyle-{47}\usepackage{cmbright}\Huge\$ .