Answer
$P_{gage}$ is not applicable
$P_{abs}=18kPa=18\frac{kN}{m^2}=2.61\frac{lbf}{in^2}=2.61psi=135.03mm Hg$
Work Step by Step
$P_{gage}$ is not applicable for vacuum pressures.
$P_{abs}=P_{atm}-P_{vac}=98kPa-80kPa=18kPa$
$P_{abs}=18kPa=18\frac{kN}{m^2}$
$P_{abs}=18kPa*(\frac{1lbf/in^2}{6.895kPa})=2.61\frac{lbf}{in^2}$
$P_{abs}=2.61\frac{lbf}{in^2}=2.61psi$
$P_{abs}=18kPa*(\frac{1mm Hg}{0.1333kPa})=135.03mm Hg$
