DAY 1 You start with 4 You triple it to get 12 You subtract 2 to get 10 DAY 2 You start with 10 You triple it to get 20 You subtract 2 to get 18 DAY 3 You start with 18 You triple it to get 54 You subtract 2 to get 52... This isn't going anywhere, now is it? You're never going to reach zero, it must be a trick question.