Question 630233
<pre>
{{{drawing(300,3675/9,-8,28,-5,44,

line(0,0,10,0),line(10,0,19,26),line(19,26,20,39),line(20,39,12,39),line(12,39,0,13),line(0,13,0,0),line(20,39,10,13),line(10,13,10,0),line(10,13,0,13),
locate(5,0,W), locate(-6,6.5,H=W+3),locate(15.3,15,L=31)

)}}}

You can also do it by substituting directly into the volume formula
and waiting to divide through by 31:

VOLUME = LENGTH·WIDTH·HEIGHT
     V = L·W·H

We substitute 4030 for V, since we are given that
We substitute 31 for L, since we are given that
We leave W as it is, that is our unknown variable
We substitute (W+3) for the width, since we are given that it is 3 inches
higher than it is wide.

 4030 = 31·W·(W+3)

Divide through by 31

  130 = W(W + 3)
  130 = W² + 3W

Get 0 on the left

    0 = W² + 3W - 130

Factor the right side:

    0 = (W - 10)(W + 13)

Use zero-factor principle:

    0 = W - 10;     0 = W + 13
   10 = W         -13 = W

Discard the negative answer, and the solution is

The width is 10 inches.

Edwin</pre>