How do I solve this question about Dalton's Law of Partial Pressure?

Question

A sample of oxygen is collected in a 175 mL container over water at 15 degrees C, and the barometer reads 752.0 torr. What volume would the dry gas occupy at 770.0 torr?

Answer 1

Determine the water vapor pressure at 15C. Subtract that from the 752 torr reading of O2 + H2O to get O2-only or dry O2 pressure. (That's the Dalton's law part.) Assume the temperature stays the same (15C). Then you can use Boyle's law (P1*V1=P2*V2) to get the dry O2 volume at 770 torr.