We are teaching you skills to solve the following types of chicken and rabbits problems:

(1) Given the sum of heads and the sum of legs, find the number of animals of each type.

(2) Given the difference of heads and the sum of legs, find the number of animals of each type.

(3) Given the difference of legs and the sum of heads, find the number of animals of each type.

(4) Given the difference of heads and the difference of legs, find the number of animals of each type.

(5) There are problems similar to chickens and rabbits problems above but with three or four animals at Old Macdonald's farm.

(6) There are problems similar to chickens and rabbits problems above but with different things like three-leg stools and four-leg tables, bicycles and tricycles, octopus and sea otters, cows and ducks, spiders and dragonflies.