Open the box labeled "Apples and Oranges"
If there is an apple inside, you know there can ONLY be apples
inside because it's improperly labeled already.
Now you also know that the box labeled "Apples" is incorrect as
well because you have just found the proper apple box. Without
looking in any other box, you know the box labeled "Oranges" is
actually "Apples and Oranges" and the box labeled "Apples" is
actually "Oranges".