mole fraction is equal to partial pressure divided by the total pressure

Question

Total pressure= sum of partial pressure

use PV=nRT where n= number of moles

equation become PV/RT=n make sure to convert the temperature to Kelvin and to use 0.0821 for R. V=volume, P=total pressure

The partial pressure of CH4(g) is 0.185 atm and that of O2(g) is 0.300 atm in a mixture of the two gases.
a) What is the mole fraction of each gas in the mixture?
b) If the mixture occupies a volume of 11.5 L at 65 degress C, calculate the total number of moles of gas in the mixture.

answered below.