a: =>3/2x=64/15

=>x=128/45

b: =>-1/6x=7/12

=>x=-7/2

c: =>11/2*x=1/2

=>x=1/2:11/2=1/11

a, \(\dfrac{x}{12}-\dfrac{5}{6}=\dfrac{1}{12}\)

\(\Rightarrow\dfrac{x}{12}=\dfrac{1}{12}+\dfrac{5}{6}\)

\(\Rightarrow\dfrac{x}{12}=\dfrac{11}{12}\)

\(\Rightarrow x=11\)

b, \(\dfrac{2}{3}-1\dfrac{4}{15}x=\dfrac{-3}{5}\)

\(\Rightarrow\dfrac{2}{3}-\dfrac{19}{15}x=\dfrac{-3}{5}\)

\(\Rightarrow\dfrac{19}{15}x=\dfrac{2}{3}+\dfrac{3}{5}\)

\(\Rightarrow\dfrac{19}{15}x=\dfrac{19}{15}\)

\(\Rightarrow x=1\)

c, \(-2^3+0,5x=1,5\)

\(\Rightarrow-8+\dfrac{1}{2}x=\dfrac{3}{2}\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{3}{2}+8\)

\(\Rightarrow\dfrac{1}{2}x=\dfrac{19}{2}\)

\(\Rightarrow x=19\)

1) \(\dfrac{x}{12}-\dfrac{5}{6}=\dfrac{1}{12}\) 2)\(\dfrac{2}{3}-1\dfrac{4}{15}x=\dfrac{-3}{5}\) \(\dfrac{x}{12}=\dfrac{1}{12}+\dfrac{5}{6}\) \(\dfrac{2}{3}-\dfrac{19}{15}x=\dfrac{-3}{5}\) \(\dfrac{x}{12}=\dfrac{11}{12}\) \(\dfrac{19}{15}x=\dfrac{2}{3}-\left(\dfrac{-3}{5}\right)\) => \(x=11\) \(\dfrac{19}{15}x=\dfrac{19}{15}\) => \(x=1\) 3) -2³ + 0,5x = 1,5 -8 + 0,5x = 1,5 0,5x = 1,5 - (-8) 0,5x = 9,5 x = 9,5 : 0,5 x = 19

=>1/2:(0,5x-1,5)=0,2-0,35=-0,15=-3/20

=>0,5x-1,5=1/2:(-3/20)=-1/2*20/3=-10/3

=>0,5x=-10/3+3/2=-11/6

=>x=-11/3

\(\dfrac{5}{4}+\left(2x-\dfrac{1}{2}\right)=\dfrac{5}{6}\\ =>2x-\dfrac{1}{2}=\dfrac{5}{6}-\dfrac{5}{4}\\ =>2x-\dfrac{1}{2}=\dfrac{10}{12}-\dfrac{15}{12}\\ =>2x-\dfrac{1}{2}=-\dfrac{5}{12}\\ =>2x=-\dfrac{5}{12}+\dfrac{1}{2}\\ =>2x=-\dfrac{5}{12}+\dfrac{6}{12}\\ =>2x=\dfrac{1}{12}\\ =>x=\dfrac{1}{12}:2\\ =>x=\dfrac{1}{12}\cdot\dfrac{1}{2}\\ =>x=\dfrac{1}{24}\)

__

\(\dfrac{3}{2}-\left(x+\dfrac{1}{4}\right)=\dfrac{5}{8}\\ =>x+\dfrac{1}{4}=\dfrac{3}{2}-\dfrac{5}{8}\\ =>x+\dfrac{1}{4}=\dfrac{12}{8}-\dfrac{5}{8}\\ =>x+\dfrac{1}{4}=\dfrac{7}{8}\\ =>x=\dfrac{7}{8}-\dfrac{1}{4}\\ =>x=\dfrac{7}{8}-\dfrac{2}{8}\\ =>x=\dfrac{5}{8}\)

__

\(\dfrac{x}{3}=\dfrac{12}{x}\\ =>x^2=3\cdot12\\ =>x^2=36\\ =>x^2=6^2\\ =>x=\pm6\)

Tìm x: 

a) \(\dfrac{5}{4}+\left(2x-\dfrac{1}{2}\right)=\dfrac{5}{6}\)

\(=>2x-\dfrac{1}{2}=\dfrac{5}{6}-\dfrac{5}{4}\)

\(=>2x-\dfrac{1}{2}=\dfrac{-5}{12}\)

\(=>2x=\dfrac{-5}{12}+\dfrac{1}{2}\)

\(=>2x=\dfrac{1}{12}\)

\(=>x=\dfrac{1}{12}:2\)

\(=>x=\dfrac{1}{24}\)

b) \(\dfrac{3}{2}-\left(x+\dfrac{1}{4}\right)=\dfrac{5}{8}\)

\(=>x+\dfrac{1}{4}=\dfrac{3}{2}-\dfrac{5}{8}\)

\(=>x+\dfrac{1}{4}=\dfrac{7}{8}\)

\(=>x=\dfrac{7}{8}-\dfrac{1}{4}\)

\(=>x=\dfrac{5}{8}\)

c) \(\dfrac{x}{3}=\dfrac{12}{x}\)

Ta có: \(x.x=3.12\)

\(\Rightarrow x^2=36\)

Vậy x = 6 hoặc x = -6

Chúc bạn học tốt

`@` `\text {Ans}`

`\downarrow`

`a)`

\(\dfrac{5}{4}+\left(2x-\dfrac{1}{2}\right)=\dfrac{5}{6}\)

`=>`\(2x-\dfrac{1}{2}=\dfrac{5}{6}-\dfrac{5}{4}\)

`=>`\(2x-\dfrac{1}{2}=-\dfrac{5}{12}\)

`=>`\(2x=-\dfrac{5}{12}+\dfrac{1}{2}\)

`=>`\(2x=\dfrac{1}{12}\)

`=>`\(x=\dfrac{1}{24}\)

Vậy, `x = 1/24`

`b)`

\(\dfrac{3}{2}-\left(x+\dfrac{1}{4}\right)=\dfrac{5}{8}\)

`=>`\(x+\dfrac{1}{4}=\dfrac{3}{2}-\dfrac{5}{8}\)

`=>`\(x+\dfrac{1}{4}=\dfrac{7}{8}\)

`=>`\(x=\dfrac{7}{8}-\dfrac{1}{4}\)

`=>`\(x=\dfrac{5}{8}\)

Vậy, `x = 5/8`

`c)`

\(\dfrac{x}{3}=\dfrac{12}{x}\)

`=>`\(x\cdot x=12\cdot3\)

`=> x^2 = 36`

`=> x^2 = (+-6)^2`

`=> x = +-6`

Vậy, `x \in {6; -6}.`

`@` `\text {Kaizuu lv uuu}`

Bài 1 : 

\(=\dfrac{2}{11}+\dfrac{4}{11}-\dfrac{6}{11}-\dfrac{3}{8}-\dfrac{5}{8}=0-1=-1\)

Bài 2 : 

\(\Rightarrow3+x=8\Leftrightarrow x=5\)

Bài 3 : 

\(\Leftrightarrow x-\dfrac{5}{11}=\dfrac{5}{4}\Leftrightarrow x=\dfrac{35}{44}\)

Bài 4 : 

Trong 2 ngày An đọc được số quyên phần quyên sách 

\(\dfrac{1}{11}+\dfrac{8}{11}=\dfrac{9}{11}\)( quyển sách ) 

đs : 9/11 quyển sách 

=>0,2x+0,4-0,5x=0,25-0,5x+0,25

=>0,2x+0,4=0,5

=>0,2x=0,1

=>x=1/2

Ta có :

\(0,5\times x-\dfrac{2}{3}\times x=\dfrac{5}{12}\)

\(\Rightarrow\dfrac{1}{2}\times x-\dfrac{2}{3}\times x=\dfrac{5}{12}\)

\(\Rightarrow x\times\left(\dfrac{1}{2}-\dfrac{2}{3}\right)=\dfrac{5}{12}\)

\(\Rightarrow x\times\dfrac{-1}{6}=\dfrac{5}{12}\)

\(\Rightarrow x=\dfrac{-5}{2}\)

Vậy \(x=\dfrac{-5}{2}\) là giá trj cần tìm

~ Chúc bn học tốt ~

\(\dfrac{-5}{2}\)

Tìm x:

a, x+30%=-1,3

<=> x+0,3=-1,3

<=> x=-1,3-0,3

<=> x=-1,6

Vậy x=-1,6

b, 0,5x-\(\dfrac{2}{3}x\) =\(\dfrac{7}{12}\)

<=>\(\dfrac{-1}{6}x\)=\(\dfrac{7}{12}\)

<=> x=\(\dfrac{-7}{2}\)

Vậy x=\(\dfrac{-7}{2}\)