conversations.from: human
conversations.value: Rachel is twice as old as Rona and Collete's age is half the age of Rona's. If Rona is 8 years old, what is the difference between the age of Collete and Rachel?
  Solve it.
conversations.from: assistant
conversations.value: Rachel's age is 8 x 2 = 16.
  Collete's age is 8 / 2 = 4.
  Therefore the difference between their age is 16 - 4 = 12.