a) 1/2 - (3/4 - 5/6)

<=> 1/2 - (3/4 - 5/6) + x = 1 - x + x

<=> x + 7/12 = 1

<=> x = 1 - 7/12

<=> x = 5/12

=> x = 5/12

b) 1/4 - x = 1/3 - 1/5

<=> 1/4 - x = 5/15 - 3/15

<=> 1/4 - x = 2/15

<=> x = 2/15 - 1/4

<=> x = 7/60

=> x = 7/60

c) 5/3 - 3/4 + x = 7/12

<=> 20/12 - 9/12 + x = 7/12

<=> 11/12 + x = 7/12

<=> x = 7/12 - 11/12

<=> x = -1/3 (sau khi rút gọn)

=> x = -1/3

Lời giải:

a. 

$\frac{2}{3}x-\frac{7}{6}=\frac{12}{7}-\frac{1}{2}=\frac{17}{14}$

$\frac{2}{3}x=\frac{17}{14}+\frac{7}{6}=\frac{50}{21}$

$x=\frac{50}{21}: \frac{2}{3}=\frac{25}{7}$

b.

$(1\frac{1}{2}+\frac{5}{3}-\frac{1}{6}):x=\frac{3}{4}-\frac{1}{2}$

$3:x=\frac{1}{4}$

$x=3: \frac{1}{4}=12$

Cái dấu chéo / là gì vậy bạn ( có phải la dấu GTTĐ | ko)

dấu chéo / là giá trị tuyệt đối đó bạn

a ) \(\left|x+4\right|=\frac{7}{3}\)

\(\Rightarrow\orbr{\begin{cases}x+4=\frac{7}{3}\\x+4=-\frac{7}{3}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{19}{3}\\x=\frac{5}{3}\end{cases}}\)

   Vậy \(x\in\left\{\frac{19}{3};\frac{5}{3}\right\}\)

b)​\(2\cdot\left|x+5\right|=\frac{8}{5}\)

   \(\left|x+5\right|=\frac{4}{5}\)

\(\Rightarrow\orbr{\begin{cases}x+5=\frac{4}{5}\\x+5=-\frac{4}{5}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{29}{5}\\x=\frac{21}{5}\end{cases}}\)

 Vậy \(x\in\left\{\frac{29}{5};\frac{21}{5}\right\}\)

c) \(\frac{4}{5}:3\cdot\left|x-1\right|=\frac{7}{2}\)

   \(\frac{4}{15}\cdot\left|x-1\right|=\frac{7}{2}\)

   \(\left|x-1\right|=\frac{105}{8}\)

\(\Rightarrow\orbr{\begin{cases}x-1=\frac{105}{8}\\x-1=-\frac{105}{8}\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=\frac{113}{8}\\x=-\frac{97}{8}\end{cases}}\)

Vậy \(x\in\left\{\frac{113}{8};-\frac{97}{8}\right\}\)

a, ( 8x - 3 ) ( 3x + 2 ) - ( 4x + 7 ) ( x + 4 ) = ( 2x + 1 ) ( 5x - 1 )

 ( 24x² + 16x - 9x - 6 ) - ( 4x² - 16x - 7x + 28 ) = 10x² - 2x + 5x -1

24x² + 16x - 9x - 6 -4x² - 16x - 7x - 10x² + 2x - 5x = 6 + 28 - 1

10x² -19x = 33

10x² - 19x -33 = 0 \(\Leftrightarrow\)10x( x+ 3 ) + 11 ( x- 3 ) = 0

=>  ( x- 3 ) ( 10x + 11 ) = 0\(\Rightarrow\orbr{\begin{cases}x=3\\x=\frac{-11}{10}\end{cases}}\)

b, 4( x - 1 ) ( x + 5 ) - ( x + 2 ) ( x + 5 ) = 3( x - 1 ) ( x + 2 )

4( x² - 5x - x + 5 ) - ( x² + 5x + 2x + 10 ) = 3( x² + 2x - x - 2 )

4x² - 20x - 4x + 20 - x² - 5x - 2x - 10 = 3x² + 6x - 3x - 6

( 4x² - x² ) + ( -20x - 4x - 5x - 2x ) + 20 - 10 = 3x² + ( 6x - 3x ) - 6

3x² - 31x - 3x² - 3x = -6-10

-34x = -16

x = \(\frac{8}{17}\)

`-7/8+2/3:x=3/5×(-5/12)`

`=> -7/8+2/3:x=-1/4`

`=> 2/3:x=-1/4 - (-7/8)`

`=> 2/3:x=-1/4 +7/8`

`=> 2/3:x=5/8`

`=>x= 2/3 : 5/8`

`=>x= 2/3 xx 8/5`

`=>x= 16/15`

a: 9-25=7-x-(25+7)

=>7-x-25-7=-16

=>-x-25=-16

=>x+25=16

hay x=-9

b: \(10+2\left|x\right|=2\cdot\left(3^2-1\right)\)

\(\Leftrightarrow2\left|x\right|=2\cdot8-10=6\)

=>x=3 hoặc x=-3

c: -6x=18

nên x=18:(-6)=-3

Ta có : x² - 2x - (x + 3)² = 6

<=> x² - 2x - x² - 6x - 9 = 6

<=> -8x - 9 = 6 

=> -8x = 15

=> x = \(\frac{15}{-8}\)