What have you tried with so far?

I got the pressure of O2 by calculating 741.5 - 27.1 mm Hg = 714.4 mm Hg

Then i converted it to atm so i got 0.94 atm as the pressure of O2 in atm.

I then used the PV=nRT equation to get moles ("n")

(0.94 atm)(0.8655 L) = n(0.0821 Latm/Kmol)(300.2K)

0.033 mol = n

I dont really know what to do after finding the moles !

Thanks for your help