(x+21)-75=39
x+21 = 39 + 75
x+21 = 114
x = 114 - 21
x = 93
vậy........
11(x-9)=781
x-9 = 781 : 11
x-9 = 71
x = 71 + 9
x = 80
vậy.........
280:(x-8)=14
x-8 = 280 : 14
x-8 = 20
x = 20 + 8
x = 28
vậy......
6(x+41)=600
x+41 = 600 : 6
x+41 = 100
x = 100 - 41
x = 59
vậy.............
15 ( x-9)=1050
x-9 = 1050 : 15
x-9 = 70
x = 70 + 9
x = 79
vậy..........
1 , ( x + 21 ) - 75 = 39
x + 21 =39+75
x + 21 =114
x =114 - 21
x = 93 Vậy x=93
2, 11(x-9)=781
x-9=781/11
x-9=71
x=71+9
x =80
Vậy x =80
3) 280/ (x-8)=14
x-8 =280/14
x-8 =20
x=20+8
x=28
Vậy x =28