In the case of the Hidden Pair pattern, there are two values in a given row, column, or box that can go into exactly two cells, but other candidates are also present in these cells, hiding the real ones among others.
Check out the example below! Observe that in the fourth row, the numbers 2 and 9 can only fit into two cells, which are highlighted in dark. Yet, there are other values - 3, 6, and 7 in the fifth column, and number 4 in the seventh - that seem to fit into these cells. Because 2 and 9 can exclusively fit into these two cells, it indicates that these cells must be 2 and 9. We don't know which one is 2 and which one is 9, but we can eliminate all other values from these cells.
After eliminating the other values, the two hidden values will remain. In the example above, after this elimination, only one cell remained in the fourth row where the value 4 is a candidate, specifically the cell in the eighth column, resulting in an immediate simple result. If you don't have an immediate simple result, you can proceed with other methods.
2/page · Hard #1 in the free sample, move 5. Open the app at this move and step through it.