Each shelf of a bookcase contained 12 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but the last one contained 8 books and that last shelf contained 3 books, how many shelves does the bookcase have?	Choose the correct answer:
A) 4 B) 5 C) 6 D) 7 E) 8
Let x be the number of shelves.   12x - 21 = 8(x-1) + 3   4x = 16   x= 4   The answer is 4.
<result>A</result>
Each shelf of a bookcase contained 12 books. If the librarian took out 21 books and rearranged the remaining books so that all shelves but the last one contained 8 books and that last shelf contained 3 books, how many shelves does the bookcase have?