In Boyle's law the volume and pressure is inversely proportional, as the volume decreases also the pressure increases, when the volume increases the pressure decreases.
first, let use the Boyle's law equation V1P1 = V2P2, where ,
V1 = the initial volume
P1 = the intial pressure
V2 = the final volume
P2 = the final pressure
they must be inversely proportional at constant temperature.
V1 = 1.5 L
P1 = 0.95 atm
V2 = 0.75 L ( change 1/2 to decimal)
V2 = ?
since the unknown is the P2 which is the final pressure then, use this formula of finding final pressure:
P2 = V1P1 / V2
= (1.5 L)(0.95 atm) / (0.75 L)
= 1.9 atm
therefore , the final pressure is needed to reduce it's volume 1/2 is 1.9 atm