conversations.from: human
conversations.value: Solve the following math problem: Tom plants 10 trees a year.  Every year he also chops down 2 trees a year.  He starts with 50 trees.  After 10 years 30% of the trees die.  How many trees does he have left?
conversations.from: assistant
conversations.value: He gets 10-2=8 new trees a year
  After 10 years he has 8*10=80 new trees
  So he had 80+50=130 trees
  He lost 130*.3=39 trees
  That means he had 130-39=91 trees