conversations.from: human
conversations.value: Break down this math problem: A set of 7 spoons costs $21. If each spoon would be sold separately, how much would 5 spoons cost?
conversations.from: assistant
conversations.value: A set of 7 spoons costs $21, so one spoon from the set costs 21 / 7 = $3.
  So if sold separately, 5 spoons would cost 5 * 3 = $15.