This would be the correct answer for a direct proportion. However, the numbers need to satisfy $\displaystyle{y}=\frac{{k}}{{x}}\usepackage{cmbright}\Huge\$ , an inverse variation equation. For the first triangle, $\displaystyle{10}=\frac{{k}}{{6}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{k}={60}\usepackage{cmbright}\Huge\$ . Substitute 15 and 9.

$\displaystyle{15}=\frac{{k}}{{9}}\usepackage{cmbright}\Huge\$ does not yield $\displaystyle{k}={60}\usepackage{cmbright}\Huge\$ , so this is not an inverse relationship.