conversations.from: human
conversations.value: Solve the following math problem: You can lower the price by 20% if you buy more than fifteen units of iPhone cases. If you pay $500 to buy 18 units, what is the original price?
conversations.from: assistant
conversations.value: If you buy 18 units, the percentage of the total price drops to 100% - 20% = 80%
  If 80% is equal to $500, then 100% is equals 100%/80% * $500 = $625