A mixture of 94.6g of O2 and 82.2g of Ne is placed in a 200.0L container at 250K .

What is the partial pressure of O2 in atmospheres?

Just ignore the Ne.

n = mols O2 = grams/molar mass = ?
Then use PV = nRT, substitute and solve for pO2.

Note: The partial pressure of Ne can be determined exactly the same way. The total pressure then is the sum of the two partial pressures OR you can add mols O2 to mols Ne, plug total mols into PV = nRT and calculate total P of the system. This will give you the same number as the sum of the two partial pressures.