Multiply both sides of the equation by 3:

$\displaystyle{3}\cdot\frac{{x}}{{3}}={3}\cdot{9}\usepackage{cmbright}\Huge\$ or $\displaystyle\frac{{3}}{{3}}\cdot{x}={27}\usepackage{cmbright}\Huge\$ or $\displaystyle{x}={27}\usepackage{cmbright}\Huge\$ .