Each shelf of a bookcase contained 11 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but one contained 8 books and the last shelf contained 11 books, how many shelves does the bookcase have?  Select the correct option.
A) 8 B) 6 C) 4 D) 3 E) 2
Let x be the number of shelves.   No of books in the beginning =11*x   After taking out 21 books No of remaining books = 11x -21   when the remaining books are rearranged, each shelf except the last shelf has 8 books and the last shelf has 11 books. So No of remaining books is also equal to 8*(x-1)+11   11x-21=8(x-1)+11   3x=24   x=8. 8nswer 8
<result>A</result>
Each shelf of a bookcase contained 11 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but one contained 8 books and the last shelf contained 11 books, how many shelves does the bookcase have?