The number of feet changed from rabbit to chicken increased, while the number of feet changed from rabbit to chicken decreased. The analysis of the significance of the problem shows that:

Chickens are less than rabbits: (100-86)÷2=7 (minus these feet, chickens and rabbits are mixed together).

Number of chickens: (100-7× 4) ÷ (2+1) ÷ 2 =12 —— (The number of feet of two chickens is equal to that of a rabbit).

Number of rabbits: 12+7= 19.

So there are 12 chickens and 19 rabbits.