Each clock represents 2 hours, so:

Trey worked $\displaystyle{2}\cdot{7}={14}\usepackage{cmbright}\Huge\$ hours

Callie worked $\displaystyle{2}\cdot{4}={8}\usepackage{cmbright}\Huge\$ hours

Will worked $\displaystyle{2}\cdot{5}={10}\usepackage{cmbright}\Huge\$ hours