V = gas volume
P = Pressure
The volume of a gas in a container varies inversely as the pressure on the gas.
V =k/p
Use the known values v=216, p=5 to find k
216 =k/5
216 x 5 = k
1,080 =k
Now we have:
V= 1,080/p
The volume if the pressure is increased by 7 pounds: (5+7=12)
V = 1,080/12
V= 90 cubic inches