9 Multiplication Table Secret (easy)!!!!!!!

This way i search in google but find only with fingers. Maybe this my discoveries :D

The easiest way to calculate 9x with - :

1x9=9 (10-1=9)

2x9=18 (20-2=18)

3x9=27 (30-3=27)

4x9=36 (40-4=36)

5x9=45 (50-5=45)

6x9=54 (60-6=54)

7x9=63 (70-7=63)

8x9=72 (80-8=72)

9x9=81 (90-9=81)

10x9=90 (100-10=90)

11x9=99 (110-11=99)

12x9=108 (120-12=108)

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14365x9=129285 (143650-14365=129285)

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Who know this way, comment.