conversations.from: human
conversations.value: Mary uses plastic grocery bags that can hold a maximum of twenty pounds. She buys 4 pounds of green beans, 6 pounds milk, and twice the amount of carrots as green beans. How many more pounds of groceries can Mary fit in that bag?
  How to solve this?
conversations.from: assistant
conversations.value: First find the total weight of the carrots: 4 pounds * 2 = 8 pounds
  Now add the total weight of each item: 6 pounds + 8 pounds + 4 pounds = 18 pounds
  Now subtract the total weight of the groceries from the bag's weight limit: 20 pounds - 18 pounds = 2 pounds