If $\displaystyle{h}=\usepackage{cmbright}\Huge\$ the number of hours, then she is charged $\displaystyle{9}{h}\usepackage{cmbright}\Huge\$ dollars plus the $50. So $\displaystyle{9}{h}+{50}={200}\usepackage{cmbright}\Huge\$ . Subtract 50 from both sides: $\displaystyle{9}{h}={150}\usepackage{cmbright}\Huge\$ . Divide both sides by 9: $\displaystyle{h}={16}\frac{{2}}{{3}}\usepackage{cmbright}\Huge\$ . She cannot rent the car for a fraction of an hour, so she can rent it for at most 16 hours.