conversations.from: human
conversations.value: Marj has two $20 bills, three $5 bills, and $4.50 in loose coins in her wallet. If she buys a cake that costs $17.50, how much money will be left in her wallet?
  How to solve this?
conversations.from: assistant
conversations.value: Two $20 bills amount to $20 x 2 = $40.
  Three $5 bills amount to $5 x 3 = $15.
  So, Marj has $40 + $15 + $4.50 = $59.50 in her wallet.
  If she buys a cake, she will be left with $59.50 - $17.50 = $42.