conversations.from: human
conversations.value: I need help with this problem:
  The total cost of Olivia’s groceries was $42. The bananas cost her $12, the bread cost her $9, and the milk cost her $7. The only other groceries she bought were apples. In dollars, how much money did the apples cost her?
conversations.from: assistant
conversations.value: The combined cost of the bananas, bread, and milk was 12 + 9 + 7 = $28.
  The difference between this and the total is the cost of the apples, which must have therefore cost Olivia 42 – 28 = $14.