conversations.from: human
conversations.value: Leo collects stickers. Two years ago, he had 100 stickers in his collection. Last year, Leo collected 50 stickers. This year, he collected twice the number of stickers as the previous year. How many stickers does Leo have in his collection?
  Solve it.
conversations.from: assistant
conversations.value: Last year, Leo had 100 +50 = 150.
  This year, he collected 2 x 50 = 100.
  Therefore, Leo had 150 + 100 = 250 stickers in his collection.