I have another question. I've tried it and i keep getting it wrong.

Question

The average kinetic energy of a 1.85-g sample of argon gas in a 3.00-L bulb is 1.28e-22 J/atom.

What is the pressure of the gas?

What is the root mean square velocity of the argon atoms under these conditions?

The average kinetic energy per molecule (or atom, in this case) is (3/2) k T, where k is the Boltzmann constant.
k = 1.36*10^-25 atm*L/K
That tells you that T = 627 K
You know that the number of moles present is
n = 1.85 g/39.94 g/mole = 0.0463 moles
Use those values of n and T and the ideal gas law to compute P = nRT/V.
The rms velocity can be obtained from the average kinetic energy and the mass of an Ar atom
Average KE = (1/2)*M^Vrms^2

i get another wrong answer

It would help if you show your work, and what you consider to be the "right" answer

P= (0.0463*0.082*627)/3 = 0.79 atm

my teacher says i'm wrong but he isn't tlling me the right answer either