Solution: (2) School B sends one more car than School A. (3) If each school adds one person to participate in the competition, there will be as many cars, so School A adds one car, so every car in School A is full of 15 people.

Similarly, starting from (4), there is a school bus B, 12 people.

Because there are as many students in the science competition in school A as in school B, we can get the equation.

Set up a school to send x school buses,

From the meaning of the title, it is15x =13x+12.

The solution is x=6.

So 15x= 15*6=90.

A: There were 90 participants.