Use the distributive property on both sides: $\displaystyle{12}{v}+{20}\le{6}{v}+{8}\usepackage{cmbright}\Huge\$

Subtract 20 from both sides: $\displaystyle{12}{v}\le{6}{v}-{12}\usepackage{cmbright}\Huge\$

Subtract $\displaystyle{6}{v}\usepackage{cmbright}\Huge\$ from both sides: $\displaystyle{6}{v}\le-{12}\usepackage{cmbright}\Huge\$

Divide both sides by 6: $\displaystyle{v}\le-{2}\usepackage{cmbright}\Huge\$