\(a)\frac{x}{4}-\frac{3}{7}+\frac{2}{5}=\frac{31}{140}\)

\(\Leftrightarrow\frac{x}{4}-\frac{1}{35}=\frac{31}{140}\)

\(\Leftrightarrow\frac{x}{4}=\frac{1}{4}\Leftrightarrow x=1\)

\(b)\frac{5}{12}+\frac{5}{x}-\frac{1}{8}=\frac{1}{12}\)

\(\Leftrightarrow\frac{5}{x}+\frac{7}{24}=\frac{1}{12}\)

\(\Leftrightarrow\frac{5}{x}=-\frac{5}{24}\Leftrightarrow x=-24\)

\(B=2\cdot4\cdot6\cdot8\cdot20=\left(6\cdot20\right)\cdot2\cdot4\cdot8=120\cdot2\cdot4\cdot8\)

mà 120 chia hết cho 30 (120 : 30 = 4)

=> B chia hết cho 30

Vậy B có chia hết cho 30

\(\frac{1}{2}\times\left(x-\frac{4}{5}\right)+\frac{3}{4}x=\frac{5}{12}\)

\(\Leftrightarrow\frac{1}{2}x-\frac{2}{5}+\frac{3}{4}x=\frac{5}{12}\)

\(\Leftrightarrow\frac{1}{2}x+\frac{3}{4}x=\frac{5}{12}+\frac{2}{5}\)

\(\Leftrightarrow\frac{5}{4}x=\frac{49}{60}\)

\(\Leftrightarrow x=\frac{49}{75}\)

Vậy \(x=\frac{49}{75}\)

bạn ơi sao lại có 2/5 vâỵ

phá ngoặc  \(\frac{1}{2}\times\frac{4}{5}=\frac{4}{10}=\frac{2}{5}\)  nhé bạn

`a,`

\((- 5) .x + 17 = - 23\)

`\Rightarrow (-5)x = -23 - 17`

`\Rightarrow (-5)x =-40`

`\Rightarrow x = (-40) \div (-5)`

`\Rightarrow x = 8`

Vậy,` x = 8`

`b,`

\(8 + 4x = - 24\)

`\Rightarrow 4x = -24 - 8`

`\Rightarrow 4x = -32`

`\Rightarrow x = -32 \div 4`

`\Rightarrow x = -8`

Vậy, `x = -8`

`c,`

\(32 – 12 + x = -10\)

`\Rightarrow 20 + x = -10`

`\Rightarrow x = -10 - 20`

`\Rightarrow x = -30`

Vậy, `x = -30`

`d,`

\(x – 87 + 13 = - 100\)

`\Rightarrow x - 87 = -100 - 13`

`\Rightarrow x - 87 = -113`

`\Rightarrow x = -113 + 87`

`\Rightarrow x = -26`

Vậy, `x = -26.`

Ta có: \(4\left|3x-12\right|+2x=1-x\)

\(\Leftrightarrow\left|12x-48\right|=1-3x\)

\(\Leftrightarrow\left[{}\begin{matrix}12x-48=1-3x\left(x\ge4\right)\\12x-48=3x-1\left(x< 4\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}15x=49\\9x=47\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{49}{15}\left(loại\right)\\x=\dfrac{47}{9}\left(loại\right)\end{matrix}\right.\)

A=(19 5/8 : 7/12 - 13 1/4 : 7/12) .4/5

  =(19 5/8 - 13 1/4):7/12.4/5

  =51/8.12/7.4/5

  =153/14.4/5

  =306/35

A={19 5/8 :7/12-13 1/4:7/12}.4/5

={19 5/8-13 1/4}:7/12.4/5

=51/8.12/7.4/5

=153/14.4/5

=306/35

MAGICPENCIL,k hen bạn

bạn viết rõ đề ra nhé

b, \(\left|4x-8\right|=1-x\)ĐK : \(x\le1\)

TH1 : \(4x-8=1-x\Leftrightarrow5x=9\Leftrightarrow x=\dfrac{9}{5}\)( ktm )

TH2 : \(4x-8=x-1\Leftrightarrow3x=7\Leftrightarrow x=\dfrac{7}{3}\)( ktm )

b) Ta có: \(\left|4x-8\right|=1-x\)

\(\Leftrightarrow\left[{}\begin{matrix}4x-8=1-x\left(x\ge2\right)\\4x-8=x-1\left(x< 2\right)\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}4x+x=1+8\\4x-x=-1+8\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}5x=9\\3x=7\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{9}{5}\left(loại\right)\\x=\dfrac{7}{3}\left(loại\right)\end{matrix}\right.\)

Giúp mình đi các bạn

=73 nha bạn

73 cậu nha

73