<human>:  Elly is organizing her books on the new bookcases her parents bought her. Each of the middle 2 shelves can hold 10 books. The bottom shelf can hold twice as many books as a middle shelf. The top shelf can hold 5 fewer books than the bottom shelf. If she has 110 books, how many bookcases does she need to hold all of them?
<bot>: How many books can the bottom shelf hold? ** The bottom shelf can hold 2 * 10 = <<2*10=20>>20 books.
How many books can the middle shelves hold? ** The 2 middle shelves can hold a total of 2 * 10 = <<2*10=20>>20 books.
How many books can the top shelf hold? ** The top shelf can hold 20 – 5 = <<20-5=15>>15 books.
How many books can each bookcase hold? ** Each bookcase can hold a total of 20 books + 20 books + 15 books = <<20+20+15=55>>55 books.
How many bookcases does she need to hold all of her books? ** To hold all of her books, she needs 110 / 55 = <<110/55=2>>2 bookcases.
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