conversations.from: human
conversations.value: Eustace is twice as old as Milford. In 3 years, he will be 39. How old will Milford be?
  Give me a solution to this problem
conversations.from: assistant
conversations.value: Eustace’s current age must be 39 years old – 3 years = 36 years old.
  So Milford’s current age must be 36 years old / 2 = 18 years old.
  So in 3 years, Milford will be 18 years old + 3 years = 21 years old.