For this chain-of-thought reasoning and answer, what was the question?
He is able to carry 3 pounds of watermelon, grapes, and oranges because1 + 1 + 1 = 3. He can buy 17 pounds of apple because20 - 3 = 17.
 A: 17
Q: Diego can carry 20 pounds of fruit home in his bookbag. If he buys a pound of watermelon, a pound of grapes, and a pound of oranges, how many pounds of apples can he buy?