The temperatures are quoted in "degrees Kelvin"degrees Kelvin. Of course, the twist introduced is the pressure value. We know that 1*atm1⋅atm will support a column of mercury 760*mm760⋅mm high, and the pressure measurement here is 900*mm900⋅mm. This is not very realistic, as no one would measure those pressures with a mercury manometer. (Why not? Well. have you ever tried to clean up a mercury spill? Putting mercury under pressure is just asking for trouble.)
Thus P_1=900*mm*Hg=(900*mm*Hg)/(760*mm*Hg*atm^1)P1=900⋅mm⋅Hg=900⋅mm⋅Hg760⋅mm⋅Hg⋅atm1 == 1.18*atm1.18⋅atm
And P_2=180*kPa=(180*kPa)/(101.32*kPa*atm^-1)P2=180⋅kPa=180⋅kPa101.32⋅kPa⋅atm−1 == 1.78*atm1.78⋅atm
You now have consistent units, and I leave the calculation as an exercise.
