If you decreased the volume of a sample of gas by a factor of three while maintaining a constant pressure, how would the absolute temperature of the gas be affected?

According to Charle's Law the volume of the gas at constant pressure is directly proportional to its absolute temperature. We expressed this as V = kT, where k is the proportionality constant. k actually is equal to n (no. of moles) times R (universal gas constant) divided by P (pressure). It is from Ideal gas equation, PV=nRT. 

So when you decreased the volume of a sample of gas by a factor of three at constant pressure the temperature of the gas also decreases by a factor of three since volume is directly proportional to temperature at constant pressure.