There are certain pairs-of-numbers and other theories that people use to help solve Sudoku puzzles, but the pairs-of-numbers theory I am describing here I haven't seen anywhere else (and I've looked). Maybe it's original. Maybe I should patent it (I doubt there's much money to be made). Whatever. 

 

Here it is: to understand this theory, it helps to work backwards from the end product; i.e. a completed puzzle. Fig 1 shows a typical medium-easy Sudoku puzzle, with some digits filled in and most left blank. Your job is to figure out what goes in the blanks. Fig 2 shows the same puzzle with all the answers filled in. Do you see any patterns? Maybe not yet, but you will soon. Just follow the Figures and explanations in the slideshow below. 

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