Correct. Multiply the first equation by $\displaystyle-{5}\usepackage{cmbright}\Huge\$ to get: $\displaystyle-{5}{x}-{20}{y}=-{145}\usepackage{cmbright}\Huge\$

Add this to $\displaystyle{5}{x}+{6}{y}={75}\usepackage{cmbright}\Huge\$ to get: $\displaystyle-{14}{y}=-{70}\usepackage{cmbright}\Huge\$

Solve for y to get $\displaystyle{y}={5}\usepackage{cmbright}\Huge\$ and substitute this into the first equation:

$\displaystyle{x}+{4}{\left({5}\right)}={29}\usepackage{cmbright}\Huge\$ or $\displaystyle{x}+{20}={29}\usepackage{cmbright}\Huge\$ , so $\displaystyle{x}={9}\usepackage{cmbright}\Huge\$