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 7 books, how many shelves does the bookcase have?  Select the correct option
A) 5	B) 6	C) 7	D) 8	E) 9
Let x be the number of shelves.   12x - 21 = 8(x-1) + 7   4x = 20   x= 5   The answer is 5.
<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 7 books, how many shelves does the bookcase have?