First, find the volume, which is the amount of space in the room.
8 x 9x 11
=792 ft^3
Now we need to find the amount of balloons it takes to fill the room.
3 ballons:1 ft^3 = 2376 balloons: 792 ft^3
3 x 792
=2376 ballons
2376 balloons are needed to fill the office.