conversations.from: human
conversations.value: Agatha has $60 to spend on a new bike. She spends $15 on the frame, and $25 on the front wheel. What does she have left, in dollars, to spend on a seat and handlebar tape?
conversations.from: assistant
conversations.value: Agatha spends 15+25=40 dollars.
  Agatha has 60-40=20 dollars left.