[Bakhtiyar]

Gas mixture being used to simulate the atmosphere of another planet consisting of 320 mg of CH₄ , 175 mg of Ar , and 225 mg of N₂ The partial pressure of N₂ at 300K is 15.2 kPa. Calculate a) volume and b) total pressure of mixture.

A) I wanted to calculate all moles and add them , but partial pressure is only of nitrogen. I confused at this point 

B) This stage is simple 
n = n(methane) + n(argon) + n(nitrogen)
P = nRT/V

[Borek]

If you know molar fraction of a gas and its partial pressure, can you calculate total pressure?

[Bakhtiyar]

P_j = X_j × P_total

[Borek]

So if you can calculate total pressure, where is the problem?