The ideal gas law question?

Pressure of ideal ges are the same as the molar ratio of the components. So if the pressure is 24 torr and the total is 745 torr, with only water and O2 present then the pressure of the O2 is 745 - 24 = 721 torr. Now to determine the number of moles present you will have to correct for the temperature and determine that at STP.