A rectangular room 8cm along by 5cm wide contains 120x120x120m of air. Calculate the height of the room.

Answer 1

With those units, this question makes absolutely no sense.
With 8 cm by 5 cm, it would in a very small doll-house
120x120x120m is a linear unit, not volume
if you meant 120x120x120 m^3, it would be enormous
(visualize a large city block as a cube)

Fix your question.
After that, volume = length x width x height