You may have incorrectly calculated $\displaystyle{2}\cdot{{3}}^{{2}}\usepackage{cmbright}\Huge\$ by multiplying first to get $\displaystyle{{6}}^{{2}}={36}\usepackage{cmbright}\Huge\$ . The correct order of operations is exponents before multiplication, and so $\displaystyle{2}\cdot{{3}}^{{2}}={2}\cdot{9}={18}\usepackage{cmbright}\Huge\$ .