conversations.from: human
conversations.value: Will's mom gave him $74 to go shopping. He bought a sweater for $9, a T-shirt for $11 and a pair of shoes for $30. He then returned his shoes for a 90% refund.  How much money does Will have left?
  How to solve this?
conversations.from: assistant
conversations.value: Will paid $30 for his shoes but then returned them and got 90% of the money back, so he lost 10% of the money, which means 10/100 * $30 = $3 is gone.
  Will spent $9 + $11 + $3 = $23.
  Will started with $74 - $23 that he spent = $51 remaining.