Asample of oxygen gas occupies a volume of 365.2 ml. when the volume is increased to 478.2 ml, the new pressure is 241.3 torr. what was the original pressure?

Boyle's law states the relationship between pressure and volume in gases.
It states that at constant temperature, pressure of a gas is inversely proportional to its volume.
PV = k
where P - pressure, V - volume and k - constant 
P1V1 = P2V2
parameters for the 1st instance are in the left side and parameters for the second instance are on the right side 
P1 x 365.2 mL = 241.3 torr x 478.2 mL 
P1 = 316.0 torr