A/ 7 X 13 X 2 - 5 = 147 B/ 15 X 7 + 2 X 4 = 428...
Bài 12:a/ 7 x 13 x 2 - 5 = 147 b/ 15 x 7 + 2 x 4 = 428 7 x ( 13 x 2 - 5) = 147 (15 x 7 + 2) x 4 = 428 7 x 21 = 147 107 x 4 = 428