b) 259 + x = 428 – 92
259 + x= 336
x= 336 - 259
x= 77
\(x=\left(428-92\right)-259\Rightarrow x=77\)
259 + x = 428 - 92
259 + x = 336
x= 336 - 259
x= 77
259 + x = 428 - 92
259 + x = 336
x = 336 - 259 = 77
vậy x = 77
b) 259 + x = 428 – 92
259 + x= 336
x= 336 - 259
x= 77