find width of a folded rectangular box

Question

 

From each of the four corners of a rectangular piece of cardboard x inches wide and 12 inches long, a 2-inch square is cut off.  The four sides of the new figure are folded straight up to form a box that is open at the top.  If the volume of the box  is 80 cubic inches, find x.

Answer 1

A walking path is shaped like a rectangle with a width 7 times its l. What is a simplified expression for the distance betwwen opposite corners of the walking path