Here's a puzzle that's not too difficult.
.....1.7.....2.4...61..8..5.9.2.57.3.7..4..8.3.57.6.9.9..1..26...4.6.....1.8.....
Robert
my resolution: Show
+----------------------+------------------------+-------------------+
| 248 238 389 | 359-4 359 1 | 6 7 89 |
| 578 358 3789 | 6 2 379 | 4 13 189 |
| 47 6 1 | 349 379 8 | 39 2 5 |
+----------------------+------------------------+-------------------+
| 68 9 68 | 2 1 5 | 7 4 3 |
| 1 7 2 | 39 4 39 | 5 8 6 |
| 3 4 5 | 7 8 6 | 1 9 2 |
+----------------------+------------------------+-------------------+
| 9 358 378 | 1 357 347 | 2 6 47 |
| 257 235 4 | 359 6 2379 | 8 135 179 |
| 2567 1 367 | 8 3579 23479 | 39 35 479 |
+----------------------+------------------------+-------------------+
(6)r9c3 - (6=8)r4c3 - r7c3 = (8)r7c2
|| |
(7-5)r2c1 = r2c2 - (5)r7c2 = r7c5 - r1c5 = (5)r1c4 *
|| ||
(7)r9c3 - (7)r2c3
|| ||
(7)r2c6 - - -
|| \
(3)r9c3 - (3=597)r9c578 - (7=394)r3c457 *
-----------
=> -4 r1c4; ste