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.