Question

A cube shaped tissue box is made entirely of cardboard. The tissue box has a length of 5 in.

Answer 1

Since no further dimensions are given, I assume that the question is asking for the surface area of the box.

A=6$a^{2}$
A=6(25)
A=150$in^{2}$ of cardboard. 

Answer 2

A cube has equal length, height and depth.

The area of one face is 5inches * 5inches, which would equal 25inches^2.

Multiply this by 6, for the 6 faces on a cube, and we get 150inches^2 of cardboard.