conversations.from: human
conversations.value: During a staff meeting, 50 doughnuts were served. If each of the 19 staff ate 2 doughnuts, how many doughnuts are left?
conversations.from: assistant
conversations.value: The staff had eaten a total of 19 x 2 = 38 doughnuts.
  So, 50 - 38 = 12 doughnuts are left.