1,-12 + x = 5x - 20

-12 + 20 = 5x - x

8 = 4x

x = 2

2, 7x - 4 = 20 + 3x

7x - 3x = 20 + 4

4x = 24

x  = 6

3 , 5x - 7 = -21 - 2x

5x + 2x  = -21 + 7

7x = -14

x = -14 : 7 = -2

4 , x + 15  = 20 - 4x

x + 4x = 20 - 15

5x = 5

x = 5 : 5 = 1

5, 17 - x = 7 - 6x

-x + 6x = 7 - 17

5x = -10

x = -10 : 5 = -2

x-(17-8) = 5+(10-3x)

x-9=5+10-3x

x+3x=5+10+9

x+3x=24

4x=24

x=24/4

x=6

vậy x=6

em ko biết

Có bị lạc đề ko dzậy?!

Phần e, 17-{-x-[-x-(-x)]}=-16 nha mn, chỗ này thiếu:))

a/ x=80

b/ x=-9

c/ x=5

d/ x=-8

c/ x=10

a)  x-45= -15+50

x-45= 35

x=35+45

x=80

b) 2x = -35+17

2x = -18

x = -9

c) -3 (x-4)=9-12

-3(x-4)= -3

x-4= 1 

x=5

d)   -36 - 4x +15 = 11 

-36 - 4x = 11- 15

-36- 4x = -4 

4x = -36 - (-4)

4x = -36+4 = -32

x = -32 : 4

x = -8

e)  125 - ( 3x - 20 ) = 115

3x - 20 = 125 - 115 

3x -20 = 10 

3x = 10+20= 30

x = 30: 3 

x = 10 

 tick nhe ban oi

a/ (x-45) - 50 = -15

          x - 45  =  -15 + 50 

          x - 45  =  35

              x     =   35 + 45

              x     =  80

b/       2x -17  =     -35

             2x    =      -35 + 17

             2x    =     -18

               x    =     -18 : 2

              x     =    -9

a/  (x-45) - 50 = -15

x-45=-15+50

x-45=35

x=80

5-x-16=40+x

-x-x=40+16-5

(-x).2=51

-x=51/2=>x=51/2

1.x=40

2.x=10

3.x=

15-x = 4x -5 

15 + 5 = 4x + x 

5x = 20

x= 4

x - 15 = 6 + 4x 

-15 - 6 = 4x -x 

3x = -21 

x= -7

a/ => 2 - x = 22 => x = -20

b/ => x - 12 = -24 => x = -12

c/ => 11 - 26 = x - 16

   => -15 = x - 16

   => x = 1

d/ => 5x - x - 2 + 6x - 10 = 0

  => 10x - 12 = 0

  => 10x = 12

  => x = 1,2

a) 2 - x = 17 - ( - 5)

2 - x = 22

x = 2-22

x=-20

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-72 - ( 15 - x ) = -43 - (-13)

-72 - 15 + x = -43 + 13

x = -43 + 13 + 72 + 15

x = -30 + 87

x = 57

-72 - ( 15 - x ) = -43 - (-13)

-72 - 15 + x = -43 + 13

x = -43 + 13 + 72 + 15

x = -30 + 87

x = 57

- 72 - ( 15 - x ) = - 43 - ( -13 )

\(\Rightarrow\) - 72 - 15 + x = - 43 + 13

\(\Rightarrow\) - 87 + x = - 30

\(\Rightarrow\) x = 57

Study well ! >_<