This is a gas law question, so I am going to assume that you are familiar with the standard symbols that we use in Chemistry.
There are essentially two equations that you need to remember for this kind of material:
- the combined gas law (P1V1/n1T1 = P2V2/n2T2) for situations when you have a before/after set of conditions. Most books won't put "n" into the combined gas law, but I like putting it because it shows that the combined gas law is just the ideal gas law solved for R.
- the ideal gas law (PV = nRT) when you are not doing a before/after comparison
Since you are doing an after/before comparison, use the first equation (combined gas law) and list your knows. Anything that does not change in the process can be crossed out to simplify the equation
P1 = 4.0atm P2 = standard atm. pressure = 1.0atm
V1 = 652 cm3 V2 = x
n1 = ?? n2 = ?? <= but we have no reason to believe this changes, so n1 = n2
T1 = ?? T2 = ?? <= but we have no reason to believe this changes, so T1 = T2
So we cross out n and T from the combined gas law and we are left with P1V1 = P2V2... also known as Boyle's law.
At this point, it's plug and chug. Just add your numbers into the equation and solve for V2. Make sure to use units in your equation (to show they cancel) and use proper significant figures.