Hi, This is another problem I am having issues with.

A box with a lid is to be made from a rectangular piece of cardboard measuring 42 cm by 126 cm. Two equal squares of side x are to be removed from oneend, and two equal rectangles are to be removed from the other end so that the tabs can be folded to form a box with a lid. Find x such that the volume of the box is a maximum.

x = ___cm

(Type an integer or decimal rounded to the nearest tenth as needed)