Final answer:
The length of the rectangle is 2 times its width.
Step-by-step explanation:
To find how many times the rectangle's length is its width, we need to divide the length by the width. The length of the rectangle is 8x104 mm and its width is 4x104 mm. So, the ratio of the rectangle's length to its width is 8x104 mm / 4x104 mm = 2. Therefore, the rectangle's length is 2 times its width.