Author/Opus: This is the 1st puzzle from guest contributor Michael Tang. You can find more puzzles from Michael on the blog mstang’s puzzles.
Rules: Fill each row and column of the grid with the digits 1 to 5 and two blackened cells. Numbers outside the grid indicate the sum of the digits between the two blackened cells in that row or column. Blackened cells are allowed to touch. Or see here.
Answer String: Enter the 5th row from left to right, followed by a comma, followed by the 7th row from left to right. Use an X (capital letter) for each blackened square.
Time Standards (highlight to view): Grandmaster = 2:15, Master = 3:00, Expert = 6:00
Note: Follow this link for other less common Number Placement puzzles.