Final answer:
The length of the box is 8 inches.
Step-by-step explanation:
To find the length of the box, first determine the dimensions of the larger square. The problem states that the dimensions are twice the first square, so the side length of the larger square is 4 inches x 2 = 8 inches.
Since the width of the cardboard is 12 inches and squares with a side length of 8 inches are cut out of the corners, the remaining width for the box is 12 inches - 2(8 inches) = 12 inches - 16 inches = -4 inches.
However, since a negative width doesn't make sense, we can assume that the box is turned inside out, so the length of the box is 8 inches.