A sample of gas in a syringe has a volume of 7.28ml at a presure of 55.4kPa. The plunger is depressd until the presure is 94.6kPa. What is the new volume, assuming constant pressure?

You mean assuming constant Temperature.

since PV=k, you want V such that
94.6V = 55.4 * 7.28
V = 4.26 ml