3 x 15 x 7 42 July 8, 2019 16 32 64 128 Tìm x 3 x 15 7 42 (3x x-15) x 7 = 42 Tìm x biết 3 x 15 7 42 5 x 7 = 35 3 7 15 31 series 3 x-5=x+3
