+129899 7.6ft^3 = 7.6(1728 in^3) = 13132.8 in^3
So we have Volume = W * L* H
x * (x + 5) (3x - 1) = 13132.8 expand the left side
3x^3 + 14x^2 - 5x = 13132.8
3x^3 + 14x^2 - 5x - 13132.8 = 0 this is probably best solved by a computer algebra system
WolframAlpha gives the solution as about x = 14.97 in = about 15 in
So....the width is about 15 in
The length is about [ 15 + 5] = 20 in
And the height is about [ 3*15 - 1] = 44 in
[The first answer looks good ]
