It seems that there's no hidden pair or tripple. How to solve it? (I have used simple rules to get so far).
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!
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.