Use Gas Law (with handwritten solutions)

A sample of oxygen, at 2500, occupies a volume of 500 mL at 1.50 atm pressure What pressure must be applied to compress the gas to a volume of 150 mL, with no temperature change? I Calculate the number of moles of helium in a '|.00-L balloon at 2700 ' and 100 atm of pressure. If 0.55 g of a gas dissolves in 1.0 L of water at 2 atm of pressure, how much will dissolve at 4.5 atm