conversations.from: human
conversations.value: Solve the following math problem: John buys thank you cards.  He decides to buy them for people who got him Christmas and birthday presents.  He sent 20 for Christmas gifts and 15 for birthday gifts.  If each card cost $2 how much did he spend on cards?
conversations.from: assistant
conversations.value: He bought 20+15=35 cards
  So he spent 35*2=$70