@kmnagji The reason is that 5 can also appear in other columns in block 6 therefore it does not have to be in the highlighted column 7. In block 9, the 5 has to be in column 7 therefore it cannot be in column 7 in block 6 so we can remove it from column 7 in block 6.
At 1:40 number 5 is present in those 3 cells that you mention and also in block 6 where numbers that are possible in three cells in same column are 125689, 59,1258. Which 5 you decide to keep? the ones in block 6 or 9 ???? Why do you chose those in block 9???
Français
