Sudoku Tutorial
Naked Doubles (Naked Twins, Naked Pairs)

Naked doubles, pretty much self explanatory.  In this case, the naked double is
present in both a row and a box (row 7, box 9)

(as an aside, be careful if you Google the term 'naked twins'.  You might start receiving
spam from porn sites.  No kidding.)

nakeddouble.jpg

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