3 7 x 21 9 July 8, 2019 16 32 64 128 3 9 (- 7 x )= 0 9 9x 21 21 3 7 2x )= 5 2 x 9 2 x 3 7 9 21 7 x 9 )+ 21 x 3 )= 406 3 7 x 5 9 x 21 5 16 21 7 x 3 9 7 x 21 x 9 1 3 7 9 x 3 21 simplified
