24 . x – 32 . x = 145 – 255 : 51
Hướng dẫn:
24 . x – 32 . x = 145 – 255 : 51
16 . x - 9 . x = 145 - 5
(16 - 9) . x = 140
7 . x = 140
x = 140 : 7
x = 20