from the original candidates:

- Code: Select all
`*-----------------------------------------------------------*`

| 1 35 2347 | 236 8 367 | 9 24 2356 |

| 234 38 6 | 1239 139 5 | 24 7 238 |

| 2357 9 2378 | 236 367 4 | 256 1 23568 |

|------------------+--------------------+-------------------|

| 239 4 239 | 7 1369 1369 | 8 5 1269 |

| 2379 1 2379 | 3469 5 8 | 2467 249 2679 |

| 8 6 5 | 149 149 2 | 147 3 179 |

|------------------+--------------------+-------------------|

| 3459 7 349 | 8 1349 139 | 125 6 1259 |

| 469 2 489 | 5 14679 1679 | 3 89 1789 |

| 3569 358 1 | 369 2 3679 | 57 89 4 |

*-----------------------------------------------------------*

- in box 8, 4s can only go in column 5, so can be removed from r6c5
- 8 and 9 are the only candidates for r8c8 and r9c8, so those two numbers MUST go into those cells and can be removed from the rest of box 9 and also the rest of column 8 - this is called a naked pair
- 2 and 4 are the only candidates for r1c8 and r2c7 (another naked pair), so again can be removed from all other cells in box 3
- this presents another naked pair (3 and 8) in row 2, so those numbers can be eliminated from all other cells in that row
- gives another naked pair (1 and 9) in column 5
- there's an "x-wing" of 1s in columns 4 and 5 (the only two places they can go in those columns are in rows 2 and 6) so any other 1s in either of those rows can be removed
- this will allow you to place some 1s and will get you quite a bit further into the puzzle

if you can't complete from here, post again with the grid you've reached so far and you'll get more assistance