However you are not given a temperature, number of moles or volume. If someone knows how to figure it out, I'd gladly like to know.
Not needed.
PV=nRT
V,R,T are the same in both cases, so if you multiply n times 3, the pressure is just times 3. Regardless of what V,R and T happen to be.
Mathematically you can also do it with algebra.
P1V1 =
P2V2 nRT (3*n) RT
V
2=V
1, you know the original pressure (P
1). Volume and temperature and number of moles all cancel out neatly when you do the algebra.
You must remember in either way you do it (and clearly the first way is the easiest) that, that is the pressure of the new system, not the total system.
And you are correct in that R is a constant, but it is not always equal to 8.3###, it depends on the units you wish to use. Here, on the right is a table of the gas constant in other units:
http://en.wikipedia.org/wiki/Gas_constant