How to solve Sudoku Expert level fast

Play and solve Sudoku Expert or Hard level using just a simple strategy anyone can use. I forgot to mention that I was using the pencil option from the APP to write notes on it. Note also that I have fast forwarded some portions of the game video for the essence of time.

Basic Rules of playing Sudoku:
https://youtu.be/DFZU1RM6gl8

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Google App used: https://play.google.com/store/apps/details?id=easy.sudoku.puzzle.solver.free

Credits:
Background Photo: Luke Chesser on Unsplash
Music: www.bensound.com

Видео How to solve Sudoku Expert level fast канала HowTo Guy