As far as i can remember the only real equation for the gas laws is
PV=nRT
P= Pressure
V= Volume
n= number of moles
R= Gas constant = 0.0821 (L*atm)/(mol*K) or 8.314 J/(mol*K)
T= Temperature in Kelvin
You use this formula if you are given 3 out of the 4 variables and asked to find the 4th.
If you have a before and after question, as in if temperature changes what happens to the pressure at constant volume you use
(P1*V1)/T1 = (P2*V2)/T2
1 means before and 2 means after so P1 is pressure before and P2 is pressure after
*** This is essentially the first equation in a before and after form minus the n and R variables since they remain constant. ***
Anything that stays constant you remove from the equations, in this example you would remove volume so you get
P1/T1 = P2/T2
P2=(P1*T2)/T1
So the conclusion you draw is that if temperature goes up (T2>T1 and therefor T2/T1 > 1), Pressure (P2) will also go up and vice versa (when T2<T1, T2/T1 < 1, P2 would be less than P1) .
I think that is really all you need to know for an intro chem class.
