You may have solved the equation $\displaystyle{0.18}\cdot{n}={120}\usepackage{cmbright}\Huge\$ . In this problem, 120 is the base, not the amount. When you rewrite a sentence as an equation, remember that "is" becomes =, and "of" becomes multiplication. So the correct equation is $\displaystyle{n}={0.18}\cdot{120}\usepackage{cmbright}\Huge\$ . The answer is 21.6.