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a)\(2.x-138=8.9\)
\(2.x-138=72\)
\(2.x=72+138\)
\(2.x=210\)
\(x=210\div2\)
\(x=105\)
b)\(\left\{\left(6x-72\right)\div2-84\right\}.28=5628\)
\(\left(6x-72\right)\div2-84=201\)
\(\left(6x-72\right)\div2=285\)
\(6x-72=570\)
\(6x=642\)
\(x=107\)
c)\(420+65.4=\left(x+175\right)\div5+30\)
\(420+260=\left(x+175\right)\div5+30\)
\(680=\left(x+175\right)\div5+30\)
\(650=\left(x+175\right)\div5\)
\(3250=x+175\)
\(3075=x\)
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a,231 - ( x - 6 ) = 1339 : 13
=> 231 - ( x - 6 ) = 103
=> x = 6 + 231 - 103
=> x = 1 34
b,
( 3x - 21 ) : 4 + 108 = 144
=> ( 3x - 21 ) : 4 = 144 - 108
=> ( 3x - 21 ) :4 = 36
=> 3x - 21 = 36.4
=> 3x - 21 = 144
=> 3x = 144 + 21
=> 3x = 165
=> x = 165 : 3
=> x = 55
[ .... ]
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\(a,\left(2600+6400\right)-3\times x=1200\)
\(9000-3\times x=1200\)
\(3\times x=9000-1200\)
\(3\times x=7800\)
\(x=7800:3\)
\(x=2600\)
\(b,\left[\left(6\times x-72\right):2-84\right]\times28=5628\)
\(\left(6\times x-72\right):2-84=5628:28\)
\(\left(6\times x-72\right):2-84=201\)
\(\left(6\times x-72\right):2=201+84\)
\(\left(6\times x-72\right):2=285\)
\(6\times x-72=285\times2\)
\(6\times x-72=570\)
\(6\times x=570+72\)
\(6\times x=642\)
\(x=107\)
\(c,2x-138=2^3:3^2\)
\(2x-138=\frac{8}{9}\)
\(2x=\frac{8}{9}+138\)
\(2x=\frac{1250}{9}\)
\(x=\frac{1250}{9}:2\)
\(x=\frac{625}{9}\)
\(d,42x=39\times42-37\times42\)
\(42x=42\times\left(39-37\right)\)
\(42x=42\times2\)
\(42x=84\)
\(x=2\)
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a) ( 2600 + 6400 ) - 3 . x = 1200
9000 - 3 . x = 1200
3 . x = 9000 - 1200
3 . x = 7800
x = 7800 : 3
x = 2600
b) [ ( 6 . x - 72 ) : 2 - 84 ] . 28 = 5628
[ ( 6 . x - 72 ) : 2 - 84 ] = 5628 : 28
[ ( 6 . x - 72 ) : 2 - 84 ] = 201
( 6 . x - 72 ) : 2 = 201 + 84
( 6 . x - 72 ) : 2 = 285
( 6 . x - 72 ) = 285 . 2
( 6 . x - 72 ) = 570
6 . x = 570 + 72
6 . x = 642
x = 642 : 6
x = 107
c) 2 . x - 138 = 23 . 32
2 . x - 138 = 8 . 9
2 . x - 138 = 72
2 . x = 72 + 138
2 . x = 210
x = 210 : 2
x = 105
d, 42 . x = 39 . 42 - 37 . 42
42 . x = 42 . ( 39 - 37 )
42 . x = 42 . 2
\(\Rightarrow\) x = 2
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Tìm x, biết :
[( 6.x - 72 ) : 2 - 84 ] . 28 = 5628
( 6.x - 72 ) : 2 - 84 =5628:28
( 6.x - 72 ) : 2 - 84 = 201
( 6.x - 72 ) : 2 =201+84
( 6.x - 72 ) : 2 =285
6x - 72 = 285 . 2
6x - 72 = 570
6x=570+72
6x=642
x=642:6
x=107
![](https://rs.olm.vn/images/avt/0.png?1311)
[( 6x - 72 ) : 2 - 84 ] . 28 = 5628
( 6x - 72 ) : 2 - 84 = 5628 : 28 = 201
( 6x - 72 ) : 2 = 201 +84 = 285
6x - 72 = 285 . 2 = 570
6x = 570 + 72 = 642
x = 642 : 6
x = 107
Ta có: [ ( 6 . x - 72 ) : 2 - 84 ] . 28 = 5628
( 6 . x - 72 ) : 2 - 84 = 5628 : 28
( 6 . x - 72 ) : 2 - 84 = 201
( 6 . x - 72 ) : 2 = 201 + 84
( 6 . x - 72 ) : 2 = 285
6 . x - 72 = 285 . 2
6 . x - 72 = 570
6 . x = 570 + 72
6 . x = 642
x = 642 : 6
x = 107
Vậy x = 107
\(a.2.x-138=2^3.3^2\)
\(2.x-138=8.9\)
\(2.x-138=72\)
\(2.x\) \(=72+138\)
\(2.x\) \(=210\)
\(x\) \(=210:2\)
\(x\) \(=105\)
\(b.231-\left(x-6\right)=1339:13\)
\(231-\left(x-6\right)=103\)
\(x-6=231-103\)
\(x-6=128\)
\(x\) \(=128+6\)
\(x\) \(=134\)
\(c.\left[\left(6.x-72\right):2-84\right].28=5628\)
\(\left[\left(6.x-72\right):2-84\right]\) \(=5628:28\)
\(\left(6.x-72\right):2-84\) \(=201\)
\(\left(6.x-72\right):2\) \(=201-84\)
\(\left(6.x-72\right):2\) \(=117\)
\(6.x-72\) \(=117.2\)
\(6.x-72\) \(=234\)
\(6.x\) \(=234+72\)
\(6.x\) \(=306\)
\(x\) \(=306:6\)
\(x\) \(=51\)
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