conversations.from: human
conversations.value: There are 516 cars in a parking lot. One-third are blue, one-half are red, and the rest are black. How many black cars are on the lot?
  Solve it.
conversations.from: assistant
conversations.value: Blue = 516 * (1/3) = 172 cars
  Red = 516 * (1/2) = 258
  Black = 516 - (172 + 258) = 86
  There are 86 black cars on the lot.