An ideal gas has a density of 1.75 kg/m3 at a gauge pressure of 160 kPa. What must be the gauge pressure if a density of 1.0 kg/m3 is desired at the same temperature?

The zeroth law of thermodynamics:  If two systems are in thermal equilibrium with a third system, then they are in thermal equilibrium with each other.

Boyle's law: The volume of a gas is inversely proportional to the absolute pressure applied to it when the temperature is kept constant.
Charles's law: The volume of a given amount of gas is directly proportional to the absolute temperature when the pressure is kept constant.
Gay-Lassac's law: At constant volume, the absolute pressure of a gas is directly proportional to the absolute temperature.