Correct. Set up a proportion with corresponding sides and solve: $\displaystyle\frac{{500}}{{20}}=\frac{{300}}{{n}}\usepackage{cmbright}\Huge\$

$\displaystyle{500}{n}={6},{000}\usepackage{cmbright}\Huge\$

$\displaystyle{n}={12}\usepackage{cmbright}\Huge\$