So do I but for a different reason. I guess some people never played baseball with less then 18 people like we used to do. Puzzles like that always make way to many assumptions. Then again I could just be lazy.
I searched for ‘baseball rules’ and that mentioned it.
Edward I think it is fair to assume that ‘two full teams’ means ‘two normal sized full teams.’
However, in the spirit of the puzzle I think it should be possible to find the answer without knowing that there are 18 playes in two teams:
If the size is smaller than 18, there will be no solutions. If the size is large enough to permit any other interesting cases, there will be no unique solution.