50 points

what is the volume of this?

The volume is 30.

You need to subtract the volume of the smaller box from that of the bigger box. It is written as such:
V = (3*3*4) -(2*1*3)
V = 36 -6
V = 30

Just for fun, i will do it differently

big rectangular box (including the missing portion) in lower right

= length x width x height

= 3 x 3 x 4

= 36ft^3

"missing" box at lower right = 1 x 3 x 2

= 6ft^3

so the ans = big box volume - missing box volume

= 36 - 6

= 30ft^3