conversations.from: human
conversations.value: A trolley driver picked up 10 people on his 1st stop.  On the next stop, 3 people got off and twice as many people from the 1st stop got on.  On the third stop, 18 people got off and 2 got on.  How many people are currently on the trolley?
  Solve it.
conversations.from: assistant
conversations.value: Between the trolley driver and his first 10 customers, there are 1+10 = 11 people are currently on the trolley
  On his first stop, 10 people go on and twice as many people got on at the second stop so 10*2 = 20 people got on at the second stop.
  So at the second stop he had 11 people on board, 3 got off and 20 got on so he now has 11-3+20 = 28 people
  At his third stop 18 people got off and 2 got on so in total there are 28-18 +2 = 12 people on the trolley