conversations.from: human
conversations.value: There were 21 dollars in the cookie jar. Doris spent $6 from the cookie jar. Martha spent half as much as Doris. How much money, in dollars, was left in the cookie jar?
  Give me a solution to this problem
conversations.from: assistant
conversations.value: Martha spent 6/2=3 dollars.
  Martha and Doris spent 6+3=9 dollars.
  There were 21-9=12 dollars left in the cookie jar.