r9c3 should reduce from 257 to 25 (7 is impossible because 7 in r9c8, r9c9), but I don't think it is very helpful ...
Thanks!
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storm_norm wrote:familiar with a skyscraper?
take a look at the 6's that i have marked.
imagine placing a 6 in either r9c6 or r8c7
what happens to the other 6's?? you will find a contradiction.
you can thus eliminate the 6's in r9c6 and r8c7.