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[Newbie]

Hey Sudoku experts,

I always get stuck at this stage. Please advise on the next several clues to crack it. Thanks.

X9X XXX 328
3X6 2X4 975
XX2 X9X XX6

X63 951 7X2
279 X4X 561
1X5 726 X93

XXX X3X 6XX
63X 4XX 2XX
9X7 XXX X34

[David Bryant]

Start by examining row 7. You can see a "7" and a "9" in the bottom left 3x3 box. You can also see a "7" and a "9" in column 4 and in column 8. So the only two spots where these values can fit in row 7 is at r7c6 & r7c9. In other words the pair of values {7, 9} must occupy the two cells r7c6 & r7c9 in some order. (This is called a "hidden pair".)

Now consider the value "2". There's already a "2" in column 1, in column 3, in column 4 and in column 8. The "2" can't go in r7c6 or r7c9, either, because those two cells are filled by {7, 9}. The only place a "2" can fit in row 7, therefore, is at r7c2. After that you can quickly place a "2" at r9c6, and you should be on your way. dcb