This is a logical reasoning problem, which is mentioned in the fourth grade math textbook of Hua Primary School. Study it yourself.

When I was in primary school, I made many hats, drawers, chickens and rabbits in the same cage. There seem to be some fishbones or something. That's disgusting. . . Some are super difficult. . . At that time, I could only do binary linear equations. . . o(╯□╰)o