Subtract 6 from both sides of the inequality: $\displaystyle{3}{x}+{6}-{6}\le{9}-{6}\usepackage{cmbright}\Huge\$ or $\displaystyle{3}{x}\le{3}\usepackage{cmbright}\Huge\$

Divide both sides by 3: $\displaystyle\frac{{{3}{x}}}{{3}}\le\frac{{3}}{{3}}\usepackage{cmbright}\Huge\$ or $\displaystyle{x}\le{1}\usepackage{cmbright}\Huge\$