conversations.from: human
conversations.value: Don buys recyclable bottles in a small town. Shop A normally sells him 150 bottles, shop B sells him 180 bottles and Shop C sells him the rest. How many bottles does Don buy from Shop C if he is capable of buying only 550 bottles?
  Find the solution.
conversations.from: assistant
conversations.value: Between Shop A and Shop B he buys 150 bottles+180 bottles=330 bottles
  Thus he can buy 550 bottles-330 bottles=220 bottles from shop C