Sudoku Solution Path    Copyright © Kevin Stone R1C4 can only be <4> R7C3 can only be <1> R3C2 is the only square in row 3 that can be <1> R3C3 is the only square in row 3 that can be <3> R5C2 is the only square in row 5 that can be <3> R8C8 is the only square in row 8 that can be <3> R8C6 is the only square in column 6 that can be <4> Squares R3C7 and R8C7 in column 7 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.    R2C7 - removing <68> from <6789> leaving <79>    R5C7 - removing <8> from <4789> leaving <479>    R7C7 - removing <6> from <46> leaving <4> R5C8 is the only square in row 5 that can be <4> Squares R1C6<28>, R2C5<268> and R3C5<268> in block 2 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.    R2C4 - removing <6> from <136> leaving <13>    R2C6 - removing <268> from <12368> leaving <13> Intersection of block 2 with column 5. The value <6> only appears in one or more of squares R1C5, R2C5 and R3C5 of block 2. These squares are the ones that intersect with column 5. Thus, the other (non-intersecting) squares of column 5 cannot contain this value.    R7C5 - removing <6> from <256> leaving <25>    R8C5 - removing <6> from <2569> leaving <259> Squares R2C1 and R8C1 in column 1 and R2C9 and R8C9 in column 9 form a Simple X-Wing pattern on possibility <2>. All other instances of this possibility in rows 2 and 8 can be removed.    R2C2 - removing <2> from <2489> leaving <489>    R8C2 - removing <2> from <25678> leaving <5678>    R2C5 - removing <2> from <268> leaving <68>    R8C5 - removing <2> from <259> leaving <59>    R2C8 - removing <2> from <256789> leaving <56789> Squares R2C3 and R5C3 in column 3 and R2C7 and R5C7 in column 7 form a Simple X-Wing pattern on possibility <9>. All other instances of this possibility in rows 2 and 5 can be removed.    R2C2 - removing <9> from <489> leaving <48>    R5C5 - removing <9> from <89> leaving <8>    R2C8 - removing <9> from <56789> leaving <5678> R2C5 can only be <6> R6C6 can only be <6> R4C6 can only be <3> R3C5 can only be <2> R7C5 can only be <5> R1C6 can only be <8> R2C6 can only be <1> R8C5 can only be <9> R2C4 can only be <3> R9C6 can only be <2> R8C2 is the only square in row 8 that can be <5> R8C3 is the only square in row 8 that can be <7> R5C3 can only be <9> R5C7 can only be <7> R2C3 can only be <8> R2C7 can only be <9> R2C2 can only be <4> R1C8 can only be <2> R1C2 can only be <9> R7C8 can only be <6> R2C9 can only be <5> R2C1 can only be <2> R2C8 can only be <7> R6C9 can only be <8> R6C1 can only be <4> R6C2 can only be <7> R4C9 can only be <1> R7C2 can only be <2> R3C8 can only be <8> R8C7 can only be <8> R3C7 can only be <6> R9C8 can only be <1> R9C4 can only be <6> R4C8 can only be <9> R8C9 can only be <2> R8C1 can only be <6> R4C4 can only be <7> R6C8 can only be <5> R6C4 can only be <9> R8C4 can only be <1> R4C1 can only be <8> R9C2 can only be <8> R4C2 can only be <6> [Puzzle Code = Sudoku-20180613-VeryHard-074811]