The given information and the equation $\displaystyle{y}={k}{x}\usepackage{cmbright}\Huge\$ give you $\displaystyle{66}={k}{\left({12}\right)}\usepackage{cmbright}\Huge\$ . Solve to find $\displaystyle{k}={5.5}\usepackage{cmbright}\Huge\$ . Now substitute this and $\displaystyle{y}={154}\usepackage{cmbright}\Huge\$ into $\displaystyle{y}={k}{x}\usepackage{cmbright}\Huge\$ :

$\displaystyle{154}={5.5}{x}\usepackage{cmbright}\Huge\$

$\displaystyle{x}={28}\usepackage{cmbright}\Huge\$

Kyra will need to babysit 28 hours.