(1) After adjustment, the books on the three-tier shelf are equal.
That is, the number of books on each floor now = 27 ÷ 3 = 9 (books)
(2) Because five books were taken out from the first floor and put on the second floor.
So the original number of books on the first floor = 9+5 = 14 (this)
(2) Because the third floor took out three books and put them on the second floor.
So the original number of books on the third floor = 9+3 = 12 (book)
(3) Since five books were taken from the first floor and put on the second floor, three books were taken from the third floor and put on the second floor.
So the result is that there are books on the second floor = 9-(5+3) = 1 (Ben).