You know its almost 2 am and i just got off from studying "Heredity and Evilotion" In BIo and i just thought to come here while having my midnight snack, then i now see your question and even tho ive done so much math in this week, i still want to answer you.....
so , as the ball are next to each other, its fig, would be like...
so here the height of cylinder (h)= 1.25x3 =3.75 inches
radius or cylinder = radius of ball = r= 1.75inches
V left in can = V of (can - 3b***s)
=Pi*r2h- 3* 4*Pi*r3/3
Its always to take common, makes the calculation easier...
=Pi*r2(h - 3*4r/3)
=22/7 * (1.75)2 ( 3.75 - 12*1.75/3)
i guess you can do the rest yourself,
just a tip: while solvinf such problem which have decimal quite a lot in them , its always better to take them in fraction , it makes the calculation easier and you are less prone to errors....
hope it helps.....
+11912 
