a) (x - 20) : 312 = 214
x - 20 = 214 x 312
x - 20 = 66768
x = 66768 + 20
x = 66788
vậy x = 66788
b) (x + 37) : 11 = 47
x + 37 = 47 x 11
x + 37 = 517
x = 517 - 37
x = 480
vậy x = 480
c)(78876 : 9) + x = 10127
8764 + x = 10127
x = 10127 - 8754
x = 1363
vậy x = 1363