You may have incorrectly distributed the 9 and gotten $\displaystyle{27}{y}-{2}\usepackage{cmbright}\Huge\$ , instead of $\displaystyle{27}{y}-{18}\usepackage{cmbright}\Huge\$ , and then incorrectly computed $\displaystyle{27}\cdot{2}-{2}\usepackage{cmbright}\Huge\$ by subtracting first, instead of multiplying. The correct answer is 36.