Each shelf of a bookcase contained 11 books. If the librarian took out 31 books and rearranged the remaining books so that all shelves but the last one contained 7 books and that last shelf contained 4 books, how many shelves does the bookcase have?  Answers:  A) 5  B) 6  C) 7  D) 8  E) 9
Let x be the number of shelves.   11x - 31 = 7(x-1) + 4   4x = 28   x = 7   The answer is 7.
<result>C</result>
Each shelf of a bookcase contained 11 books. If the librarian took out 31 books and rearranged the remaining books so that all shelves but the last one contained 7 books and that last shelf contained 4 books, how many shelves does the bookcase have?