conversations.from: human
conversations.value: John decides to learn how to play the piano.  He buys a piano for $500.  He then hires a teacher for 20 lessons at $40 per lesson but ends up getting a 25% discount.  How much did everything cost?
  Work out the solution step by step.
conversations.from: assistant
conversations.value: The normal price of the lessons would be 20*40=$800
  The discount saves him 800*.25=$200
  So the lessons cost him 800-200=$600
  That means everything costs 500+600=$1100