Correct. Multiply the second equation by 2: $\displaystyle-{2}{r}-{4}{s}+{6}{t}={6}\usepackage{cmbright}\Huge\$

Add the first equation to get: $\displaystyle-{s}+{5}{t}={11}\usepackage{cmbright}\Huge\$

Multiply the first equation by 2: $\displaystyle{4}{r}+{6}{s}-{2}{t}={10}\usepackage{cmbright}\Huge\$

Add the third equation to get: $\displaystyle{s}+{3}{t}={13}\usepackage{cmbright}\Huge\$

Add the two new equations: $\displaystyle{8}{t}={24}\usepackage{cmbright}\Huge\$ , so $\displaystyle{t}={3}\usepackage{cmbright}\Huge\$

Substitute into the previous equation: $\displaystyle{s}+{9}={13}\usepackage{cmbright}\Huge\$ , so $\displaystyle{s}={4}\usepackage{cmbright}\Huge\$

Use these values to find r and check your solution in all three equations.