a) \(70-\left(x-3\right)=45\)

\(x-3=70-45\)

\(x-3=25\)

\(x=25+3\)

\(x=28\)

b) \(12+\left(5+x\right)=20\)

\(5+x=20-12\)

\(5+x=8\)

\(x=8-5\)

\(x=3\)

c) \(130-\left(100+x\right)=25\)

\(100+x=130-25\)

\(100+x=105\)

\(x=105-100\)

\(x=5\)

d) \(175+\left(30-x\right)=200\)

\(30-x=200-175\)

\(30-x=25\)

\(x=30-25\)

\(x=5\)

e) \(\left(x+12\right)+22=92\)

\(x+12=92-22\)

\(x+12=70\)

\(x=70-12\)

\(x=58\)

f) \(95-\left(x+2\right)=45\)

\(x+2=95-45\)

\(x+2=50\)

\(x=50-2\)

\(x=48\)

a)

70 - (x - 3) = 45

x - 3 = 70 - 45 = 25

x = 25 + 3 = 28

Vậy x = 28

b)

12 + (5 + x) = 20

5 + x = 20 - 12 = 8

x = 8 - 5 = 3

Vậy x = 3

c)

130 - (100 + x) = 25

100 + x = 130 - 25 = 115

x = 115 - 100 = 15

Vậy x = 15

d)

175 + (30 - x) = 200

30 - x = 200 - 175 = 25

x = 30 - 25 = 5

Vậy x = 5

e)

(x + 12) + 22 = 92

x + 12 = 92 - 22 = 70

x = 70 - 12 = 58

Vậy x = 58

f)

95 - (x + 2) = 45

x + 2 = 95 - 45 = 50

x = 50 - 2 = 48

Vậy x = 48

câu c sai r kìa bạn

a. 420+65×4=(x+175):5+30

(x+175):5+30=420+260

(x+175):5+30=680

(x+175):5=650

x+175=3250

x=3075

b.(32×15):2=(x+70):14-40

(x+70):14-40=480:2

(x+70):14-40=240

(x+70):14=280

x+70=3920

x=3850

~~~~~~~~~~~ai đi ngang qua nhớ để lại k ~~~~~~~~~~~~~ 

~~~~~~~~~~~~ Chúc bạn sớm kiếm được nhiều điểm hỏi đáp ~~~~~~~~~~~~~~~~~~~

~~~~~~~~~~~ Và chúc các bạn trả lời câu hỏi này kiếm được nhiều k hơn ~~~~~~~~~~~~

mik khỏi chép lại đề nha

a) 680 = (x + 175) : 5 + 30

    (x + 175) : 5 = 680 - 30

    (x + 175) : 5 = 650

     x + 175 = 650 x 5

     x + 175 = 3250

     x = 3250 - 175

     x = 3075

b) 240 = (x + 70) : 14 - 40

   (x + 70) : 14 = 240 + 40

   (x + 70) : 14 = 280

    x + 70 = 280 x 14

    x + 70 = 3920

    x = 3920 - 70

    x = 3850

tk mik nha b

     x + 175 = 130

     x =

hai dòng cuối b cứ coi là ko có đi ha

mik bấm lộn

a)13-2(x+1)=7

  2.(x+1)=13-7

  2.(x+1)=6

  x+1=6/2

  x+1=3 

  x=3-1

  x=2

a, 13 - 2 ( x + 1 ) = 7

          2 .( x + 1 ) = 13 - 7
          2 .( x + 1 ) = 6
                x + 1   = 6 : 2
                x + 1    = 3
                x          = 3 - 1
                x           = 4

b)6x+2.4=5².2

6x+2=50

6x=48

x=8

c)420+65.4=(x+175):5+30

(x+175):5+30=680

(x+175):5=650

x+175=3250

x=3075

Bài 3: 

a: Ta có: 60-3(x-2)=51

\(\Leftrightarrow x-2=3\)

hay x=5

b: Ta có: \(4x-20=25:2^2\)

\(\Leftrightarrow4x=\dfrac{25}{4}+20=\dfrac{105}{4}\)

hay \(x=\dfrac{105}{16}\)

c: Ta có: \(8\cdot6+288:\left(x-3\right)^2=50\)

\(\Leftrightarrow288:\left(x-3\right)^2=50-48=2\)

\(\Leftrightarrow\left(x-3\right)^2=144\)

\(\Leftrightarrow\left[{}\begin{matrix}x-3=12\\x-3=-12\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=15\\x=-9\end{matrix}\right.\)

\(420+65\times4=\frac{x+175}{5}+30\)

\(\frac{x+175}{5}=420+260-30\)

\(\frac{x+175}{5}=650\)

\(x+175=650\times5\)

\(x+175=3250\)

x = 3250 - 175

x = 3075

a)420+65x4=(x+175):5+30

420+260=(x+175):5+30

680=(x+175):5+30

680-30=(x+175):5

650=(x+175):5

650x5=x+175

3250=x+175

x=3250-175

x=3075

a) 3636:(12x-91) =36

12x-91 = 3636:36

12x-91=101

12x=101+91

12x=192

x=192:12

x=16

b) (x : 23+45).67=8911

(x : 23+45)=8911:67

(x : 23+45)=133

x:23=133-45

x:23=88

x=88.23

x=2024

c) 420+65.4 =(x+175):5+30

420+260=(x+175):5+30

680=(x+175):5+30

(x+175):5=680-30

(x+175):5=650

(x+175)=650x5

(x+175)=3250

x=3250-175

x=3075

d) (32.15):2=(x+70):14-10

480:2=(x+70):14-10

240=(x+70):14-10

(x+70):14=240+10

(x+70):14=250

(x+70)=250.14

(x+70)=3500

x=3500-70

x=3430

e)x-4867=(175.2-50.70):25+23

x-4867=(350-3500):25+23

x-4867=-3150:25+23

x-4867=-126+23

x-4867=-103

x=-103+4867

x=4764

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)\(420+65.4=\left(x+175\right)\div5+30\)

\(420+260=\left(x+175\right)\div5+30\)

\(680=\left(x+175\right)\div5+30\)

\(650=\left(x+175\right)\div5\)

\(3250=x+175\)

\(3075=x\)

a) 2 * x - 138 = 72

    2 * x          = 72 + 138

    x                = 210 \ 2

    x                = 105

Mk thay x=y nha!!!

a)2xy-138=8x9

2xy-138=72

2xy=72+138

2xy=210

y=210:2

y=105

b){(6xy-72):2-84)}x28=5628

{(6xy-72):2-84)}x28=5628

{(6xy-72):2-84=201

{(6xy-72):2=285

(6xy-72)=570

6y=570+72

6y=642

=>y=107

c)420+65x4=(y+175):5+30

680=(y+175):5+30

650=(y+175):5

3250=y+175

y=3250-175

y=3075

a) 420 + 65.4 = (x+175):5+30                          b) x - 4867 = (175.2050.70):25+23

(x+175):5+30 = 420 + 65.4                                 x - 4867 = 1004523

(x+175):5+30 = 680                                            x = 999656

(x+175):5 = 650

x+175 = 3250

x = 3075

a) 420 + 65.4 = ( x + 175 ) : 5 + 30

   420 + 260 = ( x + 175 ) : 5 + 30

    680 = ( x + 175 ) : 5 + 30

    680 - 30 = ( x + 175 ) : 5

    650 = ( x + 175 ) : 5

    650 . 5 = x + 175

     3250 = x + 175

     x = 3250 - 175

     x = 3075

(5^2.x+175):5+30=420+260

<=>(5^2.x+175):5=650

<=>5^2.x+175=3250

<=>25.x=3075

<=>x=123

( 5² . x + 175 ) : 5 + 30 = 420 + 65 . 4

= ( 25 . x + 175 ) : 5 + 30 = 420 + 260

( 25 . x + 175 ) : 5 + 30 = 680

( 25 . x + 175 ) : 5 = 680 - 30

( 25 . x + 175 ) : 5 = 650

25 . x + 175 = 650 . 5

25 . x + 175 = 3250

25 . x = 3250 - 175

25 . x = 3075

x = 3075 : 25

x = 123

(5^2 x X +175):5 +30 =420 + 65x4

=> (25 x X +175):5 +30= 680

=>(25 x X +175):5 = 650

=>25 x X +175=3250

=>25x X= 3075

=>X=123

Vậy x = 123