Answer
The width and height increase by $4$ inches every time, while the length stays at $16$ inches.
The formula for volume is:
$\text{volume}= \text{length} \times \text{width} \times \text{height}$
Work Step by Step
If you look at the photo, the starting width and height is at 12 inches and the length is at 16 inches.
The next one has the width and height at 16 inches and length at 16 inches.
The last one has the width and height at 20 inches and length at 16 inches.
If you subtract $12$ from $16$, the answer is $4$.
If you subtract $16$ from $20$, you will also get $4$.
Thus, the height and the width increase by $4$ inches each time.
The volume can be found multiplying the length, width, and height.
