The "Hidden Triples" solving method is very similar to the "Hidden Pairs," and the core concept is the same.
A "Hidden Triples" occurs when three cells within a single row, column, or 3x3 block are the only ones that contain a specific set of three candidate numbers. These three cells may also contain other candidates, which can then be removed.
この方法は easier to understand if you look at the example.
Look at the highlighted cells. In this block, there are only three cells that contain the repeating candidate numbers: 5, 6, and 7. これは意味します that one of these three numbers must occupy each of these cells. No other number can be placed here. Likewise, the numbers 5, 6, and 7 cannot appear in any other cell within this 3x3 block.
After reaching this conclusion, you can remove the extra candidates from the メモ in these three cells to avoid confusion.
これは the principle of the "Hidden Triples" solving method when solving 数独.