You may have simplified $\displaystyle{{\left({2}-{8}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ incorrectly by squaring the 8 and then subtracting $\displaystyle{2}-{64}\usepackage{cmbright}\Huge\$ . You must simplify inside parentheses before doing other operations. So this part of the expression would first simplify to $\displaystyle{{\left(-{6}\right)}}^{{2}}\usepackage{cmbright}\Huge\$ .