You may have found the correct value of k, but then chose the two measurements whose sum is 216. However, the numbers need to satisfy $\displaystyle{y}=\frac{{k}}{{x}}\usepackage{cmbright}\Huge\$ , an inverse variation equation. For the given prism, $\displaystyle{36}=\frac{{k}}{{6}}\usepackage{cmbright}\Huge\$ , so $\displaystyle{k}={216}\usepackage{cmbright}\Huge\$ . Substitute 120 and 96.

$\displaystyle{120}=\frac{{k}}{{96}}\usepackage{cmbright}\Huge\$ does not yield $\displaystyle{k}={216}\usepackage{cmbright}\Huge\$ , so this is not an inverse relationship. The correct answer is 54 and 4.