The combined gas law or the ideal gas law is simply the incorporation of the three laws that was discovered. The Gay-Lussac’s Law, Boyle’s Law and Charle’s Law. Combning the three gives us PV/T = constant. If the pressure, volume, and temperature of a gas are known, we would get the universal molar gas constant. The universal molar gas constant is a physical constant defines the behavior of the gas under ideal conditions, theoretically. The universal molar gas constant will be the same fro all ideal or perfect gases.
If the pressure, volume, and temperature of a gas are known, which can most likely be found by using the ideal gas law