conversations.from: human
conversations.value: Ibrahim wants to buy an MP3 player for 120 euros and a CD for 19 euros. He has 55 euros in savings. His father participates in his purchase by giving him 20 euros. How much money does Ibrahim lack?
  Solve this problem.
conversations.from: assistant
conversations.value: The total price of the purchases is 120 + 19 = 139 euros.
  The amount of money he has after his father's help is 55 + 20 = 75 euros.
  The purchase amount is 139 euros, so he is missing 139 – 75 = 64 euros.