Start with $\displaystyle{10.8}-{20.2}={10.8}+{\left(-{20.2}\right)}\usepackage{cmbright}\Huge\$ . Since $\displaystyle{20.2}-{10.8}={9.4}\usepackage{cmbright}\Huge\$ , and $\displaystyle{20.2}>{10.8}\usepackage{cmbright}\Huge\$ , $\displaystyle{10.8}+{\left(-{20.2}\right)}=-{9.4}\usepackage{cmbright}\Huge\$ . Then add 11 to get 1.6. Finally, rewrite $\displaystyle{1.6}-{\left(-{38.5}\right)}\usepackage{cmbright}\Huge\$ as $\displaystyle{1.6}+{38.5}\usepackage{cmbright}\Huge\$ to get 40.1.