Two friends board an airliner just before departure time. There are only 12 seats left, 3 of which are aisle seats. How many ways can the 2 people arrange themselves in available seats so that at least one of them sits on the aisle?
Take a look at this:
https://www.slader.com/discussion/question/two-friends-board-an-airliner-just-before-departure-time-there-are-only-12-seats-left-4-of-which-are/
