You probably made a mistake with the placement of a decimal. Because this is a direct variation problem, solve for k, the constant of variation, using the equation $\displaystyle{y}={k}{x}\usepackage{cmbright}\Huge\$ , where $\displaystyle{y}={24}\usepackage{cmbright}\Huge\$ and $\displaystyle{x}={400}\usepackage{cmbright}\Huge\$ . Then use the k value in a new direct variation equation, where $\displaystyle{x}={350}\usepackage{cmbright}\Huge\$ , and solve for y. The correct answer is $21.