If temperature is constant and the amount of gas molecules (moles) is constant then pressure is inversely proportional to volume.
If the pressure is constant and the amount of gas molecules (moles) is constant then volume and temperature (in kelvin) are directly proportional.
If the volume is constant and the amount of gas molecules (moles) is constant then pressure and temperature (in kelvin) are directly proportional.
Volume is directly proportional to the number of moles of a gas.
One mole of any gas at sea level is 22.4 liters.