Answer: The height of the stacked boxes is 31 meters.
Explanation:
Since, the Volume of a cube = (side)³
The volume of first box = 1331 cubic meters,
⇒ (side)³ = 1331
⇒

Similarly, the side of second box = 11 meters ( Because, both boxes have the same volume )
Now, the volume of third box = 729 cubic meters
⇒ ⇒ (side)³ = 729
⇒

Thus, the height of the stacked boxes = Side of first box + side of second box + side of third box
= 11 + 11 + 9
= 31 meters.