Each shelf of a bookcase contained 12 books. If the librarian took out 19 books and rearranged the remaining books so that all shelves but one contained 8 books and the last shelf contained 9 books, how many shelves does the bookcase have? Choices:
A) 7	B) 6	C) 5	D) 8	E) 9
Let x be the number of shelves.   No of books in the beginning =12*x   After taking out 21 books No of remaining books = 12x -19   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)+9   12x-19=8(x-1)+9   4x=20   x=5. Answer 5
<result>C</result>
Each shelf of a bookcase contained 12 books. If the librarian took out 19 books and rearranged the remaining books so that all shelves but one contained 8 books and the last shelf contained 9 books, how many shelves does the bookcase have?