1.

$-7(5-x)-2(x-10)=15$

$-35+7x-2x+20=15$

$5x-15=15$

$5x=30$

$x=30:5=6$

2.

$3(x-4)-(8-x)=12$

$3x-12-8+x=12$

$4x-20=12$

$4x=12+20=32$

$x=32:4=8$

3.

$7(x-9)-5(6-x)=(-6)+11x$

$7x-63-30+5x=11x-6$

$12x-93=11x-6$

$12x-11x=93-6$

$x=87$

\(a,\dfrac{-1}{8}=\dfrac{3}{x}\\ \dfrac{3}{-24}=\dfrac{3}{x}\\ x=-24\\ b,\dfrac{x}{3}=\dfrac{3}{x}\\ x.x=3.3\\ x^2=9\\ x=\pm3\\ c,\dfrac{3}{4}.x=1\dfrac{1}{2}\\ \dfrac{3}{4}.x=\dfrac{3}{2}\\ x=\dfrac{3}{2}:\dfrac{3}{4}\\ x=2\\ d,x-\dfrac{3}{10}=\dfrac{7}{15}:\dfrac{3}{5}\\ x-\dfrac{3}{10}=\dfrac{7}{9}\\ x=\dfrac{7}{9}+\dfrac{3}{10}\\ x=\dfrac{97}{90}\\ e,\dfrac{-4}{7}-x=\dfrac{-8}{3}.\dfrac{3}{7}\\ \dfrac{-4}{7}-x=\dfrac{-8}{7}\\ x=\dfrac{-4}{7}+\dfrac{8}{7}\\ x=\dfrac{4}{7}\\ \)

f: =>x*4/7=1/5+2/3=3/15+10/15=13/15

=>x=91/60

g: =>1/3:3x=1/5-2/3=-7/15

=>3x=-5/7

=>x=-5/21

h: =>7/8x=-1/9

=>x=-1/9:7/8=-1/9*8/7=-8/63

j: =>(2,8x-50)=34

=>2,8x=84

=>x=30

nhiều quá :((

\(a,2\left(x-5\right)-3\left(x+7\right)=14\)

\(2x-10-3x-21=14\)

\(-x-31=14\)

\(-x=45\)

\(x=45\)

\(b,5\left(x-6\right)-2\left(x+3\right)=12\)

\(5x-30-2x-6=12\)

\(3x-36==12\)

\(3x=48\)

\(x=16\)

\(c,3\left(x-4\right)-\left(8-x\right)=12\)

\(3x-12-8+x=0\)

\(4x-20=0\)

\(4x=20\)

\(x=5\)

Cố nốt nha bn ! 

cảm ơn, bn nha:)))

mà hình như bạn TOP 3 trả lời câu hỏi pải ko nhỉ???

d, \(-7\left(3x-5\right)+2\left(7x-14\right)=28\)

\(\Leftrightarrow-21x+35+14x-28=28\Leftrightarrow-7x=21\Leftrightarrow x=-3\)

e, \(5\left(3-2x\right)+5\left(x-4\right)=6-4x\)

\(\Leftrightarrow15-6x+5x-20=6-4x\Leftrightarrow-5-x=6-4x\)

\(\Leftrightarrow-11+3x=0\Leftrightarrow x=\frac{11}{3}\)

f, \(-5\left(2-x\right)+4\left(x-3\right)=10x-15\)

\(\Leftrightarrow-10+5x+4x-12=10x-15\Leftrightarrow-22+9x=10x-15\)

\(\Leftrightarrow-7-x=0\Leftrightarrow x=-7\)

\(/x-\frac{1}{2}/=\frac{1}{3}\\ =>\orbr{\begin{cases}x-\frac{1}{2}=\frac{1}{3}\\x-\frac{1}{2}=-\frac{1}{3}\end{cases}}\\ =>\orbr{\begin{cases}x=\frac{1}{3}+\frac{1}{2}\\x=-\frac{1}{3}+\frac{1}{2}\end{cases}}\\ =>\orbr{\begin{cases}x=\frac{5}{6}\\x=\frac{1}{6}\end{cases}}\)

\(a,|x-\frac{1}{2}|=\frac{1}{3}\)

\(\Rightarrow\orbr{\begin{cases}x-\frac{1}{2}=\frac{1}{3}\\x-\frac{1}{2}=-\frac{1}{3}\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{5}{6}\\x=\frac{1}{6}\end{cases}}}\)

\(b,\frac{14}{15}:\frac{9}{10}=x:\frac{3}{7}\)

\(\frac{28}{27}=x:\frac{3}{7}\)

\(x=\frac{4}{9}\)

\(c,\frac{6}{5}:8=\frac{2}{5}:x\)

\(\frac{3}{20}=\frac{2}{5}:x\)

\(x=\frac{8}{3}\)

\(d,3x-\frac{7}{8}=\frac{5}{2}\)

\(3x=\frac{27}{8}\)

\(x=\frac{9}{8}\)

1)  10 - 3 ( x - 1 ) = -5

      3 ( x - 1 ) = 10 - ( - 5 )

      3 ( x - 1 ) =  15

          x - 1   = 15 : 3

          x - 1   = 5

         x         = 5 + 1

        x         = 6

2) 3x + 75 = - 15

    3x        = - 15 - 75

    3x        = - 90

      x       = -90 : 3

     x        = -30

4)  12 - ( x - 7 ) = - 8

             x - 7   = 12 - (- 8 )

             x - 7   = 20

             x        = 20 + 7

            x         = 27

5)  x + 75 = 15

    x         = 15 - 75

    x         = -60

7)  2x + 18 = 10

     2x        = 10 - 18

     2x        = -8

       x        = - 8 : 2

       x       = -4

8)  26 - 3x = 5

            3x = 26 - 5

            3x = 21

              x  = 21: 3

              x = 7

9) x - 12 = - 15

    x       = -15 + 12

   x         =-3

 10 ) 24 - 2 ( x + 5 ) = 38

              2 ( x+ 5 )  = 24 - 38

              2 ( x + 5 ) = - 14

                  x + 5    = -14 : 2

                  x + 5    = -7

                  x          = -7 - 5

                  x          = -12

còn là bạn tự làm tiếp nhé ! bạn gửi nhiều cầu qua bạn chỉ nên gửi ít một thời như vậy khó có thể giải làm bạn ạ!

25 - 5 (3- x) = 15 

25 - 5 (3-x) = 15  

      5 (3-x) = 25 -15 

      5 (3-x) = 10 

     3 - x = 10 : 5 

    3 - x = 2 

         x = 3 - 2 

          x = 1

1) |x + 2| = 4

\(\Leftrightarrow\orbr{\begin{cases}x+2=4\\x+2=-4\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=2\\x=-6\end{cases}}\)

2) 3 – |2x + 1| = (-5)

\(\Leftrightarrow\left|2x+1\right|=8\Leftrightarrow\orbr{\begin{cases}2x+1=8\\2x+1=-8\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=\frac{7}{2}\\x=\frac{-9}{2}\end{cases}}\)

3) 12 + |3 – x| = 9

\(\Leftrightarrow\left|3-x\right|=-3\)(vô lí)

=>\(x=\varnothing\) 

1) I x+2 I=4

\(\Rightarrow\orbr{\begin{cases}x+2=4\\x+2=-4\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=-6\end{cases}}}\)

2) \(3-|2x+1|=-5\)

\(\Leftrightarrow|2x+1|=8\)

\(\Leftrightarrow\orbr{\begin{cases}2x+1=8\\2x+1=-8\end{cases}\Leftrightarrow\orbr{\begin{cases}2x=7\\2x=-9\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=\frac{7}{2}\\x=\frac{-9}{2}\end{cases}}}\)

3) \(12+|3-x|=9\)

\(\Leftrightarrow|3-x|=-3\)(vô lí vì I 3-x I \(\ge\)0)

1; |\(x\) + 2| = 4

    \(\left[{}\begin{matrix}x+2=-4\\x+2=4\end{matrix}\right.\)

     \(\left[{}\begin{matrix}x=-4-2\\x=4-2\end{matrix}\right.\)

     \(\left[{}\begin{matrix}x=-6\\x=2\end{matrix}\right.\)

Vậy \(x\) \(\in\) {- 6; 2}

b)0,5x+2/3x+2/3=7/2

   1/2x+2/3x+2/3=7/2

     x(1/2+2/3)+2/3=7/12

     x.7/6+2/3       =7/12

     x.7/6              =7/12-2/3

    x.7/6               =-1/12

    x                     =-1/12:7/6

    x                    =-1/14

b)3/5-2/15:x=1/2

   2/15:x       =3/5-1/2

   2/15:x       =1/10

   x                =2/15:1/10

   x                = 4/3