You probably correctly found $\displaystyle{12}{\left(-{32}\right)}\usepackage{cmbright}\Huge\$ , but then added the $20 to this amount. It is true that the tour company added the fee, but this amount is also a debt, so you should be adding $\displaystyle-\text{\$}{20}\usepackage{cmbright}\Huge\$ to the cost of the 12 tickets.