x - 5 = 8 x 121

x - 5 = 968

 x= 968 + 5 

 x= 973

chính là A

x:8=121 ( dư 5 )

x=121x8+5

x=968+5

x=973

Đáp án:A nha

973-x:34+12=729

973-x:34=717

x:34=256

x=8704

x=8704

\(\text{Tìm }x\text{ : }\)

\(973-x\text{ : }34+12=729\)

\(973-x\text{ : }34=729-12\)

\(973-x\text{ : }34=717\)

\(x\text{ : }34=973-717\)

\(x\text{ : }34=256\)

\(x=256\cdot34\)

\(x=8704\)

\(\frac{x-971}{972}+\frac{x-973}{970}+\frac{x-975}{968}+\frac{x-977}{966}=\frac{x-972}{971}+\frac{x-970}{973}+\frac{x-968}{975}+\frac{x-966}{977}\)

\(\Rightarrow\frac{x-971}{972}-1+\frac{x-973}{970}-1+\frac{x-975}{968}-1+\frac{x-977}{966}-1=\frac{x-972}{971}-1+\frac{x-970}{973}-1+\frac{x-968}{975}-1+\frac{x-966}{977}-1\)\(\Rightarrow\frac{x-1943}{972}+\frac{x-1943}{970}+\frac{x-1943}{968}+\frac{x-1943}{966}=\frac{x-1943}{971}+\frac{x-1943}{973}+\frac{x-1943}{975}+\frac{x-966}{977}\)

\(\Leftrightarrow\frac{x-1943}{972}+\frac{x-1943}{970}+\frac{x-1943}{968}+\frac{x-1943}{966}-\frac{x-1943}{971}-\frac{x-1943}{973}-\frac{x-1943}{975}-\frac{x-966}{977}=0\)

\(\Leftrightarrow\left(x-1943\right).\left(\frac{1}{972}+\frac{1}{970}+\frac{1}{968}+\frac{1}{966}-\frac{1}{971}-\frac{1}{973}+\frac{1}{975}+\frac{1}{977}\right)=0\)

\(\Leftrightarrow\left(x-1943\right)=0\Leftrightarrow x=1943\)

Vậy...

a) (y – 1) : 105 = 125 x 80

(y – 1) : 105 = 10000

(y – 1) = 10000 x 105

(y – 1) = 1050000

y = 1050000 + 1

y = 1050001

b) (y – 607 200) : 305 = 642 + 318

(y – 607 200) : 305 = 960

(y – 607 200) = 960 x 305

(y – 607 200) = 292800

y = 292800 + 607 200

y = 900000

\(a.\left(y-1\right):105=125x80\)                   \(b.\left(y-607200\right):305=642+318\)

\(\left(y-1\right):105=10000\)                             \(\left(y-607200\right):305=960\)

\(y-1=10000x105=1050000\)                \(y=960+607200=608160\)

\(y=1050000+1=1050001\)

\(c.\left(1780-973\right)x\left(75:y\right)=2401+20\)

\(807x\left(75:y\right)=2401+20\)

\(807x\left(75:y\right)=2421\)

\(75:y=2421:807=3\)

\(y=75:3=25\)

a)  (y - 1) : 105 = 125 x 80

     (y - 1) : 105 = 10000

     (y - 1)          = 10000 x 105

     (y - 1)         = 10500000

      y                = 10500000 + 1

      y                = 10500001.

b) (y – 607 200) : 305 = 642 + 318

(y – 607 200) : 305 = 960

(y – 607 200) = 960 x 305

(y – 607 200) = 292800

 y = 292800 + 607 200

 y = 900000.

       y = 25.

       25-{14-[(2-x)-(x+13)+23]}=62-{8-[(2x-10)-(29-3x)+8]}

<=>25-14+2-x-x-13+23=62-8+2x-10-29+3x+8

<=>13-x-x-13+23=2x+3x+8-10-29

<=>-x-x+23=2x+3x+(-31)

<=>23-(x+x)=2x+2x-31

<=>23-2x=2x+3x-31

<=>23+31=2x+2x+3x

<=>54=x(2+2+3)

<=>54=x.7

=>x=54/7

Vậy x=54/7

<=>54=x.7

a, bổ sung đề 

 \(\dfrac{29-x}{21}+1+\dfrac{27-x}{23}+1+\dfrac{25-x}{25}+1+\dfrac{23-x}{27}+1+\dfrac{21-x}{29}+1=0\)

\(\Leftrightarrow\dfrac{50-x}{21}+\dfrac{50-x}{23}+\dfrac{50-x}{25}+\dfrac{50-x}{27}+\dfrac{50-x}{29}=0\)

\(\Leftrightarrow\left(50-x\right)\left(\dfrac{1}{21}+\dfrac{1}{23}+\dfrac{1}{25}+\dfrac{1}{27}+\dfrac{1}{29}\ne0\right)=0\Leftrightarrow x=50\)

1: =>x=8-35=-27

2: =>15-4+x=6

=>x+11=6

hay x=-5

3: =>-30+25-x=-1

=>x+5=1

hay x=-4

4: =>x-(-13)=-8

=>x+13=-8

hay x=-21

5: =>x-29-17+38=-9

=>x-8=-9

hay x=-1

x=1397

chúc bạn học giỏi

^^

123+x=1520

x=1520-123

x=1397

123 + x = 547 + 973

123  +x=1520

           x=1520-123

            x=1397

Đúng 100%

\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow x\left(\frac{1}{2}-\frac{2}{3}\right)=\frac{7}{12}\Rightarrow x\cdot\left(\frac{3}{6}-\frac{4}{6}\right)=\frac{7}{12}\)

\(\Rightarrow x\cdot\left(-1\right)=\frac{7}{12}\Rightarrow x=\frac{7}{12}:\left(-1\right)=\frac{7}{-12}\)

\(c,\frac{\left(x-5\right)}{12}\cdot\frac{9}{29}=\frac{-6}{29}\Rightarrow\frac{\left(x-5\right)}{12}=\frac{-6}{29}:\frac{9}{26}\)

\(\frac{\Rightarrow\left(x-5\right)}{12}=\frac{-6}{9}=\frac{-2}{3}\Rightarrow x-5=-\frac{2}{3}\cdot12\)

\(\Rightarrow x-5=\frac{-24}{3}=-8\Rightarrow x=-8+5=-3\)

\(a,0,5x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow\frac{1}{2}x-\frac{2}{3}x=\frac{7}{12}\)

\(\Rightarrow-\frac{1}{6}x=\frac{7}{12}\)

\(\Rightarrow x=-\frac{7}{2}\)

\(c,\frac{x-5}{12}\cdot\frac{9}{29}=-\frac{6}{29}\)

\(\Rightarrow\frac{x-5}{12}=-\frac{2}{3}\)

\(\Rightarrow x-5=12.\left(-\frac{2}{3}\right)\)

\(\Rightarrow x-5=-8\)

\(\Rightarrow x=-3\)

b)\(\frac{-8}{17}+\frac{5}{17}< \frac{x}{17}< \frac{-6}{17}+\frac{9}{17}\)\(\left(x\in Z\right)\)

\(\Rightarrow\frac{-3}{17}< \frac{x}{17}< \frac{3}{17}\)

\(\Rightarrow-3< x< 3\)

\(\Rightarrow x\in\left\{-2;-1;0;1;2\right\}\)

Vậy \(x\in\left\{-2;-1;0;1;2\right\}\)