Add 11 to both sides: $\displaystyle{2}{x}={7}{x}+{30}\usepackage{cmbright}\Huge\$

Subtract $\displaystyle{7}{x}\usepackage{cmbright}\Huge\$ from both sides: $\displaystyle-{5}{x}={30}\usepackage{cmbright}\Huge\$

Divide both sides by $\displaystyle-{5}\usepackage{cmbright}\Huge\$ : $\displaystyle{x}=-{6}\usepackage{cmbright}\Huge\$