a) A = 125 x a - 874 + 1256
Thay a = 967 vào A, ta có:
A = 125 x 967 - 874 +1256
A = 120875 - 874 +1256
A = 121257
b) 85506 = 125 x a - 874 + 1256
85506-1256+874 = 125 x a
85124 = 125 x a
a = 85124 : 125
a = 680,992
b)125xa-874+1256=85506
125xa-874=85506-1256
125xa=84250+874
a=85124:125
a=680.992