conversations.from: human
conversations.value: Charlie had 10 stickers. He bought 21 stickers from a store in the mall and got 23 stickers for his birthday. Then Charlie gave 9 of the stickers to his sister and used 28 to decorate a greeting card. How many stickers does Charlie have left?
  Solve this problem.
conversations.from: assistant
conversations.value: The total number of stickers is 10 + 21 + 23 = 54.
  The number of stickers given away and used on the greeting card is 9 + 28 = 37.
  Charlie has 54 − 37 = 17 stickers left.