There are x people who set up a second school to participate in the competition, and one school is (25-x) people.

15×(25-x)+3= 13x

5- 15x+3= 13x

13x+ 15x=8

5 15x+3 15x=8

8 15x=8

x= 15

25- 15= 10 (person)

A: A school has 10 participants and B school has 15 participants.