Ok so 4 boys jumped into the pool.
There was 8 girls, and some boys and in total 17 children. To find the amount of boys all you have to do is subtract 17-8 which =9. Then some boys jumped into the pool, and now there are 13 boys. So same thing, you subtract. You subtract the amount of boys that there are now to the number of boys that there were before. 13-9=4. And there’s you answer!
