Agas that exerts a pressure of 6.20 atm in a container with a bolume of __ ml will exert a pressure of 9.150 atm when transferred to a container with a volume of 322 ml.

P1V1 = P2V2

P1 = 6.20 atm
V1 -?
P2= 9.150 atm 
V2 = 322 mL

6.20 atm*V1 = 9.150 atm *322 mL

V1=9.150 atm *322 mL/6.20 atm ≈ 475 mL
V1 = 475 mL

Mass is the amount of matter in an object.  weight is the measurement of the pull of gravity on an object.  say for example, you travel to the moon which has a different gravitational field compared to the gravitational field of earth. (gravitational fields: earth = 1, moon = 0.165)  now when you are on the moon, the pull of gravity on you is different than on the earth. and as weight is the measurement of the pull of gravity on an object, that means yes, your weight can and will change on the moon.  however, on the moon, on earth or even on jupiter, the amount of mass inside of you remains the same. meaning your physical mass remains constant.  in conclusion it is possible for your weight to change as your mass remains constant.