Correct answer 16: ① Three pairs of shoes 30 get one pair of shoes10; 2 shoes +2 cats with whistles is 20, and the cat with whistles is 5; (3) A whistle is 2, and now a cat is 3; ④ So it is 10+3X2= 16. Note that the whistle on the cat's neck and the whistle in question are single whistle. Hope to adopt. Thank you!