Five birds flew from the first tree to the second tree, reducing five birds. Three of the five birds flew to the third tree. The second tree * * * added two birds, and the third tree added three birds, so the first tree has seven more birds and eight more birds than the second tree. There are 36 trees * * * That is to say, let's assume that the first tree has X birds x+(x-7)+(x-8)=36.

Solution: x= 17, the first tree has 17, the second tree has 10 and the third tree has 9.