a) \(70-5\left(2x-3\right)=45\)

\(70-10x+15=45\)

\(-10x=45-70-15\)

\(-10x=-40\)

\(x=4\)

vay \(x=4\)

 b) \(156-\left(x+61\right)=82\)

\(x+61=156-82\)

\(x+61=74\)

\(x=74-61\)

\(x=13\)

vay \(x=13\)

c) \(6\left(5x+35\right)=330\)

\(30x+210=330\)

\(30x=330-210\)

\(30x=120\)

\(x=4\)

vay \(x=4\)

d) \(936-\left(4x+24\right)=72\)

\(4x+24=936-72\)

\(4x+24=864\)

\(4x=864-24\)

\(4x=840\)

\(x=210\)

vay \(x=210\)

\(70-5.\left(2x-3\right)\)\(=45\)

\(5.\left(2x-3\right)\)\(=\)\(70-45\)

\(5.\left(2x-3\right)\)\(=25\)

\(2x-3=25:5\)

\(2x-3=5\)

\(2x=8\)

\(x=8:2\)

\(x=4\)

\(156-\left(x+61\right)\)\(=82\)

\(x+61=156-82\)

\(x+61=74\)

\(x=74-61\)

\(x=13\)

\(6.\left(5x+35\right)\)\(=330\)

\(5x+35=330:6\)

\(5x+35=55\)

\(5x=55-35\)

\(5x=20\)

\(x=20:5\)

\(x=4\)

\(936-\left(4x+24\right)\)\(=72\)

\(4x+24=936-72\)

\(4x+24=864\)

\(4x=864-24\)

\(4x=840\)

\(x=840:4\)

\(x=210\)

Tìm x :

a) 70 - 5 . ( 2x - 3 ) = 45

           5 . ( 2x - 3 ) = 70 - 45

           5 . ( 2x - 3 ) = 25

                    2x - 3 = 25 : 5

                    2x - 3 = 5

                         2x = 5 + 3

                         2x = 8

                           x = 8 : 2

                           x = 4

b)    156 - ( x + 61 ) = 82

                     x + 61 = 156 - 82

                     x + 61 =  74

                             x = 74 - 61

                             x = 13

c) 6 . ( 5x + 35 ) = 330

             5x + 35 = 330 : 6

             5x + 35 = 55

                     5x = 55 - 35

                     5x = 20

                       x = 20 : 5 

                       x = 4

d) 936 - ( 4x + 24 ) = 72

                  4x + 24 = 936 - 72

                  4x + 24 = 364

                          4x = 364 - 24

                          4x = 340

                            x = 340 : 4

                            x = 85

a) => x : 80 = 2

=> x = 160

b) => 200/15 : x = 3

=> x = 40/9

c) => 158 - x = 140

=> x = 18

d) => 231 - (x-6) = 103

=> x - 6 = 128

=> x = 134

a)   70 - 5 ( 2x-3 ) = 45

              5( 2x-3 ) = 25

                  2x - 3 = 25 : 5

                 2x - 3  = 5

                       2x = 8 

                         x = 8 : 2

                        x = 4

b)   6 ( 5x + 35 ) = 330

    5x + 35 = 330 : 6

    5x + 35 = 55

            5x = 55 - 35

            5x = 20

              x = 20 : 5

              x = 4 

c)  936 - ( 4x + 24 ) = 72

     4x + 24 = 936 - 72

     4x + 24 = 864

             4x = 864 - 24

             4x = 840

              x = 840 : 4

              x = 210

 d)   5( 3x + 34 ) = 515

             3x + 34 = 515 : 5

             3x + 34 = 103

                     3x = 103 -  34

                     3x = 69

                       x = 69 : 3

                      x = 23

\(a,70-5\left(2x-3\right)=45\)

\(\Leftrightarrow10x-15=70-45\)

\(\Leftrightarrow10x=25+15\)

\(\Leftrightarrow x=\frac{40}{10}=4\)

Vậy x=4

\(b,6\left(5x+35\right)=330\)

\(\Leftrightarrow5x+35=55\)

\(\Leftrightarrow5x=20\)

\(\Leftrightarrow x=4\)

vậy x=4

\(c,936-\left(4x+24\right)=72\)

\(\Leftrightarrow4x+24=936-72\)

\(\Leftrightarrow4x=864-24\)

\(\Leftrightarrow x=840:4=210\)

Vậy x=210

\(d,5\left(3x+34\right)=515\)

\(\Leftrightarrow3x+34=515:5\)

\(\Leftrightarrow3x=103-34\)

\(\Leftrightarrow x=69:3=23\)

Vậy x=23

a) 70 - 5.(2x-3)=45

5.(2x-3)=70-45

10x-15 =25

10x     =25 +15

10x     =40

x        =40:10

x        = 4

b)6.(5x+35) =330

5x +35 = 330 : 6

5x +35 =55

5x = 55-35

5x = 20

x = 20 : 5

x = 4

c)936-(4.x+24)=72

4x+24 =936 - 72

4x+24 =864

4x = 864 - 24

4x = 840

x = 840 :4

x = 210

d)(x+1)+(x+3)+(x+5)

x+1+x+3+x+5=30

(x+x+x)+(1+3+5) = 30

3x + 9 =30

3x = 30-9

3x =21

x = 21 : 3

x = 7

e)Vì số lượng x bằng  số số hạng nên số lượng x là :

(100 - 2) : 2 + 1 = 50 (số x)

Tổng 2 +4+6+8+...+100 là :

(100+2) x 50 : 2 = 2550

Ta có :

50 x + 2550 = 2650

50x = 2650 -2550

50x = 100

x = 100 : 50

x = 2

Tick nghen !

a) 124 + (118 - x) = 217

118 - x = 217 - 124

118 - x = 93

x = 118 - 93

x = 25

b) 156 - (x + 61) = 82

x + 61 = 156 - 82

x + 61 = 74

x = 74 - 61

x = 13

c) 219 - 7(x + 1) = 100

7(x + 1) = 219 - 100

7(x + 1) = 119

x + 1 = 119 : 7

x + 1 = 17

x = 17 - 1

x = 16

d) (3x - 6).3 = 3⁴

3x - 6 = 3⁴ : 3

3x - 6 = 3³

3x - 6 = 27

3x = 27 + 6

3x = 33

x = 33 : 3

x = 11

e) 231 - (x - 6) = 1339 : 13

231 - (x - 6) = 103

x - 6 = 231 - 103

x - 6 = 128

x = 128 + 6

x = 134

a) 124 + (118 - x) = 217

118 - x = 217 - 124

118 - x = 93

x = 118 - 93

x = 25

b) 156 - (x + 61) = 82

x + 61 = 156 - 82

x + 61 = 74

x = 74 - 61

x = 13

c) 219 - 7(x + 1) = 100

7(x + 1) = 219 - 100

7(x + 1) = 119

x + 1 = 119 : 7

x + 1 = 17

x = 17 - 1

x = 16

d) (3x - 6) . 3 = 3⁴

(3x - 6) . 3 = 81

(3x - 6) = 81 : 3

(3x - 6) = 27

3x = 27 + 6

3x = 33

x = 33 : 3 

x = 11

e) 231 - (x - 6) = 1339 : 13

231 - (x - 6) = 103

(x - 6) = 231 - 103

x - 6 = 128

x = 128 + 6

x = 134

cô cấm dùng máy tính -) 

lớp 9 ms đc dùng:_)

a. 231-(x-6)=103

-(x-6)=-128

(x-6)=128

x=134

b. 4x-7=4704-9x-2566

4x+9x=4704-2566+7

13x=2145

x=165

c. 294=6x+90

6x=204

x=34

d. 936-4x-24=72

-4x=-840

4x=840

x=210

a) 2 * x - 138 = 8 * 9

2 * x - 138 = 72

2 * x = 210

x = 105

b) 231 - ( x - 6 ) = 1339 : 13

231 - x + 6 = 103

237 - x = 103

x = 134

c) 70 - 5 * ( x-3) = 45

5 * (x-3) = 25

x - 3 = 5

x = 8

cac phan con lai bn lm tuong tu nha

* 2*X-138=8*9

   <=> 2*X-138=72

   <=> 2*X=72+138

   <=> 2*X=210

   <=> X=210/2=105

*231-(X-6)=1339:13

 <=> 231-(X-6)=103

<=> X-6=231-103

<=>X-6=128

<=>X=128+6=134

*70-5*(X-3)=45

<=>5*(X-3)=70-45

<=>5*(X-3)=25  

<=>X-3=25/5

<=>X-3=5

<=>X=8

*10+2*X=16

<=>2*X=16-10

<=>2*X=6

<=>X=6/2=3

\(2x-138=72\)

\(2x=72+138\)

\(2x=210\)

\(x=105\)

\(231-\left(x-6\right)=103\)

\(x-6=231-103\)

\(x-6=128\)

\(x=134\)

\(5\left(x-3\right)=70-45\)

\(5\left(x-3\right)=25\)

\(x-3=5\)

\(x=5+3\)

\(x=8\)

\(2x=16-10\)

\(2x=6\)

\(x=3\)

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

Trả lời

1)17-2(2x-3)=3

        2(2x-3)=17-3

        2(2x-3)=14

           2x-3 =14:2

           2x-3 =7

           2x     =7+3

           2x     =10

            x      =10:2

           x       =5

1) 17 - 2(2x - 3) = 3

=> 17 - 4x + 6 = 3

=>  23 - 4x = 3

=> 4x = 23 - 3

=> 4x = 20

=> x = 20 : 4 = 5

2) 125  - 5(3x - 1) = 25

=> 125 - 15x + 5 = 25

=> 130 - 15x = 25

=> 15x = 130 - 25

=> 15x = 105

=> x = 105 : 15

=> x = 7

3) 70 - 5(2x - 3) = 45

=> 70 - 10x + 15 = 45

=> 85 - 10x = 45

=> 10x = 85 - 45

=> 10x = 40

=> x = 40 : 10

=> x = 4

4) 231 - (x - 6) = 133 : 13

=> 231 - x + 6 = 133/13

=> 237 - x = 133/13

=> x = 237 - 133/13

=> x = 2948/13

\(1,17-2\left(2x-3\right)=3\)

\(\Rightarrow17-4x+6=3\)

\(\Rightarrow4x=20\Leftrightarrow x=5\)

\(2,125-5\left(3x-1\right)=25\)

\(\Rightarrow125-15x-5=25\)

\(\Rightarrow15x=95\Rightarrow x=3,8\)

\(3,70-5\left(2x-3\right)=45\)

\(\Rightarrow70-10x+15=45\)

\(\Rightarrow10x=45\Leftrightarrow x=4,5\)

\(4,231-\left(x-6\right)=\frac{133}{13}\)

\(\Rightarrow231-\frac{133}{13}=x-6\)

\(\Rightarrow x=237-\frac{133}{13}=\frac{2821}{13}\)