Question 316572
The original piece of cardboard has width of w and length of l=w+3


If you cut 3 inch squares from each side, you have to subtract 6 from each side (3 from each corner) to get the new dimensions:


L = (w+3-6)
W = w-6
H = 3      [ the height is 3 because when you fold up the cut corners, that gives you the height ]


Now we know that Volume = LxWxH, so let's plug everything in and solve for w:


V=LWH
264 = (w+3-6)(w-6)(3)
264 = 3(w-3)(w-6)

Do FOIL

264 = 3(w^2 -9w+18)
0 = 3w^2 -27w +54 - 264
0 = 3w^2 -27w -210
0 = 3(w^2 -9w -70)


Now you have to factor (think, what multiplies to -70 and has a difference of -9? Answer: -14 and 5.)

0 = 3(w-14)(w+5)


So we choose the positive answer, w=14.

This means the length is l=w+3 = 17


Width =14, Length =17