conversations.from: human
conversations.value: Provide a step by step solution for the following math problem: Xavier needs 84 paper plates for a housewarming party. He already has 21 green plates and 28 red plates. How many more plates should Xavier buy?
conversations.from: assistant
conversations.value: The total number of green and red plates is 28 + 21 = 49.
  Xavier should buy 84 − 49 = 35 more plates.