Check the picture below. Recall, is an open-top box, so, the top is not part of the surface area, of the 300 cm². Also, recall, the base is a square, thus, length = width = x.
so.. that'd be the V(x) for such box, now, where is the maximum point at?
now, let's check if it's a maximum point at 10, by doing a first-derivative test on it. Check the second picture below.
so, the volume will then be at
The graph of f(x) = |x| would look like the image below.
The absolute value of 2 + 7<span> is 5.</span>
W is width
W+9 is length
W+W+9=54
2w=45
45/2
W=22.5
Width is 22.5 length is 31.5
Answer is below this comment :D