Correct. Let $\displaystyle{t}=\usepackage{cmbright}\Huge\$ the number of orchestra tickets sold and $\displaystyle{b}=\usepackage{cmbright}\Huge\$ the number of balcony tickets sold. Then

$\displaystyle{t}+{b}={980}\usepackage{cmbright}\Huge\$

$\displaystyle{50}{t}+{35}{b}={44},{350}\usepackage{cmbright}\Huge\$

Multiply the first equation by $\displaystyle-{50}\usepackage{cmbright}\Huge\$ : $\displaystyle-{50}{t}-{50}{b}=-{49},{000}\usepackage{cmbright}\Huge\$

Add this to $\displaystyle{50}{t}+{35}{b}={44},{350}\usepackage{cmbright}\Huge\$ : $\displaystyle-{15}{b}=-{4},{650}\usepackage{cmbright}\Huge\$

Divide both sides by $\displaystyle-{15}\usepackage{cmbright}\Huge\$ : $\displaystyle{b}={310}\usepackage{cmbright}\Huge\$