7 8 x (- 5 3 4 July 8, 2019 16 32 64 128 7 8 x 4 5 2 3 3 8 x 5 7 x 4 6 9 8 7 6 5 x 4 3 2 1 7 4 3x )-( 8 5 x )= 4 3 x 8 3 4x 9 )+ 5 7 8 x 8 x 3 )- 5 2x 4 )= 6x 7 x 4 7 8 x 3 5 1 4 7 8x 5 3 8x 4 7 x 3 )- 5 4x 8 ( 5 x 7 8 x 4 ) 3 10 7 5 x )- 3 (- 4 6x )=- 8 17 7 8 x 19 5 8 x 3 4 air filter 3 7 8 x 4 5 16 7 x 3 )- 5 ≤ 4x 8 7 8 x 3 1 5 x 55 49
