## Step-By-Step Solution:

## Initial Grid | |

First step - add in all possible valid pencilmarks. |

For row 7, number 6 is only possible in cell (4,7) | ||

For column 9, Number 6 is only possible in cell (9,1) | ||

For column 9, Number 1 is only possible in cell (9,2) | ||

For row 2, number 4 is only possible in cell (8,2) | ||

For row 5, number 4 is only possible in cell (1,5) | ||

For row 5, number 6 is only possible in cell (6,5) | ||

For column 5, Number 4 is only possible in cell (5,9) | ||

For column 5, Number 3 is only possible in cell (5,1) | ||

For column 5, Number 1 is only possible in cell (5,6) | ||

For column 4, Number 1 is only possible in cell (4,1) | ||

For row 6, number 2 is only possible in cell (4,6) | ||

For box 3, candidates for 5 are all in column 8, so you can remove candidates from other blocks. | ||

Candidates for 5 in boxes 2 and 8 force the candidates in box 5 to be in the remaining line. | ||

Candidates for 8 in boxes 2 and 8 force the candidates in box 5 to be in the remaining line. | ||

Naked Pair for 2 and 5, can remove these as candidates from other cells. | ||

For box 7, candidates for 2 are all in column 3, so you can remove candidates from other blocks. | ||

Candidates for 5 in boxes 4 and 7 force the candidates in box 1 to be in the remaining line. | ||

Naked Pair for 5 and 8, can remove these as candidates from other cells. | ||

For box 2, candidates for 8 are all in column 6, so you can remove candidates from other blocks. | ||

Naked Pair for 7 and 8, can remove these as candidates from other cells. | ||

Naked Pair for 5 and 8, can remove these as candidates from other cells. | ||

Hidden Triple for 1, 4 and 9, can remove other candidates from these cells. | ||

For column 1, Number 3 is only possible in cell (1,9) | ||

Number 2 is the only value possible in cell (6,9). | ||

Number 3 is the only value possible in cell (6,8). | ||

Naked Triple for 7, 8 and 9, can remove these as candidates from other cells. | ||

For box 3, candidates for 7 are all in column 7, so you can remove candidates from other blocks. | ||

For blocks 8 and 9, candidates for 8 are all in the same two rows (8 and 9) | ||

Naked Pair for 2 and 5, can remove these as candidates from other cells. | ||

X-Wing in columns for 7. (X-Wings) | ||

Number 2 is the only value possible in cell (7,2). | ||

Number 5 is the only value possible in cell (8,1). | ||

Number 2 is the only value possible in cell (1,1). | ||

Number 5 is the only value possible in cell (1,2). | ||

Number 3 is the only value possible in cell (8,3). | ||

Number 7 is the only value possible in cell (7,3). | ||

Number 5 is the only value possible in cell (6,3). | ||

Number 2 is the only value possible in cell (8,7). | ||

Number 8 is the only value possible in cell (3,7). | ||

Number 7 is the only value possible in cell (3,2). | ||

Number 8 is the only value possible in cell (2,1). | ||

Number 7 is the only value possible in cell (6,1). | ||

Number 9 is the only value possible in cell (4,2). | ||

Number 8 is the only value possible in cell (6,2). | ||

Number 9 is the only value possible in cell (6,4). | ||

Number 6 is the only value possible in cell (1,4). | ||

Number 1 is the only value possible in cell (1,3). | ||

Number 6 is the only value possible in cell (2,3). | ||

Number 5 is the only value possible in cell (3,5). | ||

Number 7 is the only value possible in cell (2,4). | ||

Number 8 is the only value possible in cell (8,4). | ||

Number 5 is the only value possible in cell (5,4). | ||

Number 7 is the only value possible in cell (4,5). | ||

Number 8 is the only value possible in cell (5,5). | ||

Number 3 is the only value possible in cell (7,5). | ||

Number 9 is the only value possible in cell (9,5). | ||

Number 9 is the only value possible in cell (2,6). | ||

Number 7 is the only value possible in cell (8,6). | ||

Number 5 is the only value possible in cell (9,6). | ||

Number 4 is the only value possible in cell (2,7). | ||

Number 3 is the only value possible in cell (9,7). | ||

Number 9 is the only value possible in cell (1,8). | ||

Number 1 is the only value possible in cell (2,8). | ||

Number 2 is the only value possible in cell (3,8). | ||

Number 8 is the only value possible in cell (7,8). | ||

Number 5 is the only value possible in cell (4,8). | ||

Number 4 is the only value possible in cell (9,8). | ||

Number 5 is the only value possible in cell (2,9). | ||

Number 8 is the only value possible in cell (4,9). | ||

Number 9 is the only value possible in cell (8,9). | ||

Number 7 is the only value possible in cell (9,9). |