conversations.from: human
conversations.value: I'm completely lost with this math problem: The library has 9,900 books. Over the summer, they sold some books. If only four sixths of the books are left, how many did they sell?
  Can you give me a hand?
conversations.from: assistant
conversations.value: A sixth of the books is 9900/6 = 1650 books.
  Only 4*1650 = 6600 books are left.
  The library sold 9900-6600= 3300 books over the summer.