1)120 + ( 34 + 3x ) - ( 6 + x ) = 0

=> 120 + 34 + 3x - 6 - x = 0

=> ( 120 + 34 - 6 ) + ( 3x - x ) = 0

=> 148 + 2x = 0

=> - 2x = 148 => x = 148 : ( - 2 )

=> x = -74

Vậy x = - 74

2)\(\dfrac{-5}{6}-x=\dfrac{7}{12}+\left(\dfrac{-1}{3}\right)\)

\(=>x=\dfrac{-5}{6}-\left(\dfrac{7}{12}-\dfrac{1}{3}\right)\)

\(=>x=\dfrac{-5}{6}-\dfrac{7}{12}+\dfrac{1}{3}\)

\(=>x=\dfrac{-10}{12}-\dfrac{7}{12}+\dfrac{4}{12}\)

\(=>x=\dfrac{-10-7+4}{12}=\dfrac{-13}{12}\)

Vậy x = \(\dfrac{-13}{12}\)

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120 + (34 + 3x) + (6 + x) = 0

=> 120 + 34 + 3x + 6 + x = 0

=> (120 + 34 + 6) + (3x + x) = 0

=> 160 + 4x = 0

=> 4x = -160

=> x = -160:4

=> x = -40

120 + (34 + 3x) + (6 + x) = 0

120 + 34 + 3x + 6 + x = 0

 (120 + 34 + 6) + (3x + x) = 0

 160 + 4x = 0

 4x = -160

  x = -160:4

=> x = -40

1) 3x = 45 + 15 = 60

x = 60 : 3 = 20

2) 5x = 50 - 35 = 15

x = 15 : 5 = 3

3) (2x - 5) + 17 = 6

2x - 5 = 6 - 17

2x - 5 = -11

2x = -11 + 5

2x = -6

x = -6 : 2 = -3

4) 10 - 2(4 -3x) = -4

2(4 - 3x) = -4 - 10 = -14

4 - 3x = -14 : 2 = -7

3x = -7 - 4 = -18

x = -18 : 3 = -6

\(\left\{{}\begin{matrix}\left\{{}\begin{matrix}3x-15=45\Leftrightarrow3x=60\Leftrightarrow x=20\\35-5x=50\Leftrightarrow5x=-15\Leftrightarrow x=-3\end{matrix}\right.\\\left\{{}\begin{matrix}\left(2x-5\right)+17=6\Leftrightarrow2x+5=-11\Leftrightarrow2x=-16\Leftrightarrow x=-8\\10-2\left(4-3x\right)=-4\Leftrightarrow8-6x=14\Leftrightarrow6x=-6\Leftrightarrow x=-1\end{matrix}\right.\\\left\{{}\begin{matrix}-12+3\left(-x+7\right)=-18\Leftrightarrow-3x+21=-6\Leftrightarrow-3x=-27\Leftrightarrow x=9\\24:\left(3x-2\right)=-3\Leftrightarrow3x-2=-8\Leftrightarrow3x=-6\Leftrightarrow x=-2\end{matrix}\right.\\-45:5\left(-3-2x\right)=3\Leftrightarrow-15-10x=-15\Leftrightarrow10x=0\Leftrightarrow x=0\end{matrix}\right.\)

5) - 12 + 3(-x + 7) = -18

              3(-x+7) = -18- -12

              3(-x+7) = -30

                 -x+7 = -30 : 3

                  -x+7 = -10

                   -x    = -10 -7 = -17 

     Vậy x= 17

                   
6) 24 : (3x – 2) = -3

          ( 3x - 2)  = 24: -3 

          3x - 2 = -8 

           3x      = -8 +2

           3x      = -6 

              x     = -6:3 = -2 

Vậy x= -2
7) -45 : 5.(-3 – 2x) = 3  

             5(-3-2x) = -45: 3

              5( -3-2x) = -15 

                -3-2x      = -15 :5 

                  -3- 2x    = -3

                       2x     = -3--3

                         2x= 0

Vậy  x= 0