Use the distributive property on the right side to simplify:

$\displaystyle{12}{x}-{7}+{5}{x}={16}{x}+{8}+{x}-{8}\usepackage{cmbright}\Huge\$

Combine like terms on both sides: $\displaystyle{17}{x}-{7}={17}{x}\usepackage{cmbright}\Huge\$

Subtract $\displaystyle{17}{x}\usepackage{cmbright}\Huge\$ from both sides: $\displaystyle-{7}={0}\usepackage{cmbright}\Huge\$

Since this is a false statement, there is no solution.