140 : (x - 8)=7
7(x-8)=140
7x-56=140
7x=196
x=28

Bài 1,
a,71 - (33 + x) = 26
<=> 33 + x = 71 - 26
<=> 33 + x = 45
<=> x = 45 - 33
<=>x= 12
b, ( x + 73) - 26 = 76
<=> x + 73 = 76 + 26
<=> x + 73 = 102
<=> x = 102 - 73
<=> x = 29
c, 45 - ( x + 9 ) = 6
<=> - ( x + 9 ) = -39
<=> x + 9 = 39
<=> x = 30

d, 89 - ( 73 - x ) = 20
<=> - ( 73 - x ) = - 69
<=> 73 - x = 69
<=> x = 4
e, ( x + 7) - 25 = 13
<=> x + 7 = 38
<=> x = 31
f, 198 - ( x + 4 ) = 120
<=> - ( x + 4 ) = - 78
<=> x + 4 = 78
<=> x = 74

g, 140 : (x - 8)=7
<=> 7(x-8)=140
<=> 7x-56=140
<=> 7x=196
<=> x=28
h, 4. ( x + 41 ) = 400
<=> x + 41 = 100
<=> x = 59
i, 11 . ( x - 9) = 77
<=> x - 9 = 7
<=> x = 16

a. 71 – (33 +x) =26
33 + x =71- 26
33 + x = 45
X =45 -33
X = 12
Vậy x = 12
g. 140 : (x – 8) = 7
x – 8 = 140 :7
x – 8 = 20
x = 20 + 8
x = 28
Vậy x = 28.
 
m. 2(x-51) = 2* 2^3 + 20
2 ( x-51) = 36
x-51 = 36:2
x-51 = 18
x = 18 +51
x = 69.
Vậy x= 69.