a :
[( 10 - x ) . 2 + 5] : 3 - 2 = 3
( 10 - x ) x 2 + 5 = ( 3+2) x 3
( 10 - x ) x 2 + 5 = 15
10 -x = ( 15 -5 ) : 2
10 - x = 5
x = 5
a) \(\left[\left(10-x\right)2+5\right]:3-2=3\)
\(\left(20-2x+5\right):3-2=3\)
\(\left(20-2x+5\right):3=5\)
\(20-2x+5=15\)
\(20-2x=10\)
\(2x=10\)
\(x=5\)
b) \(6x-302=2^3\cdot5\)
\(6x=8\cdot5+302\)
\(6x=342\)
\(x=57\)
c) \(12\left(x-1\right):3=4^3-2^3\)
\(12\left(x-1\right):3=56\)
\(12\left(x-1\right)=168\)
\(x-1=12\)
\(x=13\)
a, [(10-x).2+5]:3-2=3
[(10-x).2+5]:3 =3+2
[(10-x).2+5]:3 =5
(10-x).2+5 =5.3
(10-x).2+5 =15
(10-x).2 =15-5
(10-x).2 =10
10-x =10:2
10-x =5
x =10-5
x =5
b, 6x-320=23.5
6x-320=8.5
6x-320=40
6x =40+320
6x =360
x =360:6
x =60
c, 12.(x-1):3=43-23
12.(x-1):3=64-8
12.(x-1):3=56
12.(x-1) =56.3
12.(x-1) =168
x-1 =168:12
x-1 =14
x =14+1
x =15
Mình chỉ biết làm câu C thôi nhá :
12 ( x-1 ) :3 = 4^3 + 2^3
12 ( x-1 ) :3 = 64+8
12 ( x-1 ) :3 =72
12 ( x-1 ) = 72.3
12 ( x-1 ) =216
x-1=216:12
x-1=18
x=18+1
x=19
Vậy:x=19