if the rectangles must not be squares, then they may be aligned side by side within the square.
Then 2 sides of the rectangles equal the square's side lengths,
and the other 2 sides are one quarter of the length of the square's sides.
Since 4x is 144, x is a quarter of this.
hence you can find the rectangle's perimeter from this.
If the rectangles can be squares, then the side lengths are half the square's side lengths.