Each shelf of a bookcase contained 11 books. If the librarian took out 15 books and rearranged the remaining books so that all shelves but the last one contained 7 books and that last shelf contained 12 books, how many shelves does the bookcase have?  Pick one: A) 5 B) 6 C) 7 D) 8 E) 9
Let x be the number of shelves.   11x - 15 = 7(x-1) + 12   4x = 20   x= 5   The answer is 5.
<result>A</result>
Each shelf of a bookcase contained 11 books. If the librarian took out 15 books and rearranged the remaining books so that all shelves but the last one contained 7 books and that last shelf contained 12 books, how many shelves does the bookcase have?