Answer : The final volume will be, 84.4 mL
Explanation :
Boyle's Law : It is defined as the pressure of the gas is inversely proportional to the volume of the gas at constant temperature and number of moles.

or,

where,
= initial pressure = 760 torr
= final pressure = 120 kPa = 900 torr (1 kPa = 7.5 torr)
= initial volume = 100 mL
= final volume = ?
Now put all the given values in the above equation, we get:


Therefore, the final volume will be, 84.4 mL