Asample of carbon dioxide gas, co2 (g), occupies a volume of 5.75 l at 0.890 atm. if the temperature and the number of moles remain constant, calculate the volume when the pressure
a. increased to 1.25 atm
b. decrease to 0.350 atm

According to Boyle's law;
P1V1 = P2V2
P1 is the pressure of the gas in the first case.
V1 is the volume of the gas in the first case.
P2 is the pressure of the gas in the second case.
V2 is the volume of the gas in the second case.

P1 = 0.890 atm, V1 = 5.75l

a. P2 = 1.25 atm, 
0.890*5.75 = 1.25*V2
V2 = 4.094 l

b. P2 = 0.350 atm,
0.890*5.75 = 0.350*V2
V2 = 14.621 l.

You would do 1500/4 and the answer is 375