Answer:
As pressure decreases, density decreases
Step-by-step explanation:
Pressure applied on a given system is essentially the force acting per units area of that system. Volume occupied by a system is inversely proportional to the pressure. As pressure is decreased the volume tends to increase.
Density is another property of matter which is inversely related to the volume.
i.e.

Therefore, when mass of the system is constant, decreasing the pressure will increase the volume which would in turn decrease the density.