Hidden Single
With the candidates written in, only one empty cell in the box can still take the digit.
All candidates have been entered in the empty cells.
cell A is the only place for candidate 6 in block B. Therefore, cell A is 6.
With the candidates written in, only one empty cell in the box can still take the digit.
All candidates have been entered in the empty cells.
cell A is the only place for candidate 6 in block B. Therefore, cell A is 6.