conversations.from: human
conversations.value: Mary goes with her 3 children to the circus. Tickets cost $2 for adults and $1 for children. Mary pays with a $20 bill. How much change will she receive?
  Give me a detailed solution.
conversations.from: assistant
conversations.value: Mary's ticket costs $2/ticket * 1 ticket = $2
  Mary's children's tickets cost 3 tickets * $1 = $3
  Together the tickets cost $2 + $3 = $5
  After paying with a 20-dollar bill, Mary will receive $20 - $5 = $15