I have absolutely no idea how to do this question. I've tried several different ways.. tried using the equation:
[itex]P = (1/3)*(N/V)*2*((3/2)kT)[/itex]

Then using the idea that:
[itex]P = F/A[/itex]

No luck. I think I'm doing things wrong. Does this have something to do with internal energy? ([itex]U = (3/2)nRT[/itex])