Need help knowing what formula to use...pv=nrt or (P1 x V1) / T1 = (P2 x V2) / T2?

A 10.0g- sample of a gas has a volume of 5.25L at 30 degrees celsius and 758 mm Hg .
If 2.8g of the same gas is added to this constant 5.25- volume and the temperature raised to 64 degrees celsius, what is the new gas pressure?
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