1. Let the number of pigeons on the tree be x and the number of pigeons under the tree be y..

Y- 1= 1/3(X+Y)

X- 1=Y+ 1

Answer: X=7

Y=5

2. the number of cages is x.

4X+2 & gt； 5(X- 1)+2

Answer: x

There are at most 4*4+2= 18 chickens and 4 cages.