conversations.from: human
conversations.value: John is half times younger than his father, who is 4 years older than John's mother. If John's father is 40 years old, what's the age difference between John and his mother?
  What is the solution?
conversations.from: assistant
conversations.value: John is half times his father's age. Thus 1/2*40 = 20 years.
  Since the mother is 4 years younger than the father, she is 40-4= 36 years old.
  The age difference between John and his mother is 36-20 = 16 years