7x 15 4x 5 July 8, 2019 16 32 64 128 7x 8 )-( 4x 5 )= 15 3 x 5 )= 7x 15 4x 5x 15 7x 4x 3 4x 3x 5 7x 15 4x 5 7x 4x =- 15 7 7-4x 15