Ahlyis -> Trying to understand a hint from the mobile Sum Sudoku app. (5/12/2023 4:27:06 PM)
I'm trying to understand a hint given by the mobile app for a Hard Sum sudoku puzzle.
Can anyone explain how Innies and Outies can be applied here to eliminate the 9? (NOTE: I can see a way to eliminate the 9, I just don't see how to apply Innies and Outies to do so.)