Step-by-step explanation:
Let the width be = w
The length will be = w+9
And height h = 3 inches ( side of square =3 in)
Volume = l x w x h
According to question
[tex]80 = w(w+9)3\\3w^2+27w-80=0[/tex]
So, this equation indicates that the volume of the box is 80 in.