     Sudoku Solution Path   Copyright © Kevin Stone R4C9 can only be <8> R6C6 can only be <2> R5C9 can only be <5> R6C9 can only be <4> R5C8 can only be <1> R6C4 can only be <8> R4C6 can only be <3> R4C4 can only be <6> R4C1 can only be <2> R9C6 can only be <4> R6C1 can only be <7> R1C4 can only be <2> R5C5 can only be <9> R1C6 can only be <5> R9C4 can only be <9> R1C1 is the only square in row 1 that can be <1> R3C7 is the only square in row 3 that can be <1> R7C3 is the only square in row 7 that can be <5> R2C3 is the only square in column 3 that can be <7> R2C9 is the only square in row 2 that can be <2> Squares R5C1 and R9C1 in column 1 form a simple locked pair. These 2 squares both contain the 2 possibilities <68>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the column.    R2C1 - removing <8> from <489> leaving <49>    R8C1 - removing <8> from <489> leaving <49> Squares R8C3<28>, R9C1<68> and R9C2<268> in block 7 form a comprehensive locked triplet. These 3 squares can only contain the 3 possibilities <268>. Since each of the squares must contain one of the possibilities, they can be eliminated from the other squares in the block.    R7C2 - removing <2> from <249> leaving <49> R7C8 is the only square in row 7 that can be <2> Intersection of column 8 with block 3. The value <4> only appears in one or more of squares R1C8, R2C8 and R3C8 of column 8. These squares are the ones that intersect with block 3. Thus, the other (non-intersecting) squares of block 3 cannot contain this value.    R2C7 - removing <4> from <489> leaving <89> Squares R2C1 and R7C7 form a remote locked pair. <49> can be removed from any square that is common to their groups.    R2C7 - removing <9> from <89> leaving <8> R2C5 can only be <4> R3C8 can only be <4> R1C8 can only be <7> R1C9 can only be <9> R9C8 can only be <8> R8C9 can only be <3> R2C1 can only be <9> R1C5 can only be <8> R8C5 can only be <2> R9C9 can only be <7> R9C1 can only be <6> R1C2 can only be <4> R8C1 can only be <4> R8C7 can only be <9> R7C2 can only be <9> R8C3 can only be <8> R9C5 can only be <3> R7C7 can only be <4> R9C2 can only be <2> R5C1 can only be <8> R3C2 can only be <8> R3C3 can only be <2> R5C2 can only be <6> [Puzzle Code = Sudoku-20180722-VeryHard-285980]    