First, factor out the common factor of $\displaystyle{9}{x}\usepackage{cmbright}\Huge\$ .

$\displaystyle{9}{x}{\left({x}+{3}\right)}={0}\usepackage{cmbright}\Huge\$

$\displaystyle{9}{x}={0}\usepackage{cmbright}\Huge\$ or $\displaystyle{x}+{3}={0}\usepackage{cmbright}\Huge\$

$\displaystyle{x}={0}\usepackage{cmbright}\Huge\$ or $\displaystyle{x}=-{3}\usepackage{cmbright}\Huge\$