Choose the orderings of the 3 subjects left to right on the shelf in 3! ways Choose the orderings of the 3 math books left to right in 3! ways. Choose the orderings of the 2 chemistry books left to right in 2! ways. Choose the orderings of the 2 physics books left to right in 2! ways. Answer: 3!3!2!2! = 6·6·2·2 = 144 ways Edwin