conversations.from: human
conversations.value: This math problem has got me stumped: Peter bought 4 new notebooks for school. 2 of them are green, one is black and the other one is pink. The total cost was $45. If the black notebook cost $15, and the pink one cost $10, how much did the green notebooks cost each?
  Can you show me the way?
conversations.from: assistant
conversations.value: The black and pink notebook cost a total of $15 + $10 = $25
  The green notebooks cost a total of $45 - $25 = $20
  Each green notebook cost $20 / 2 = $10