Ta có \(\frac{11}{4}\)> \(\frac{x}{20}\)> \(\frac{5}{11}\)

=>    \(\frac{605}{220}\)> \(\frac{11x}{220}\)> \(\frac{100}{220}\)

=> 605 > 11x > 100

=>  56 > x > 9

\(\frac{11}{4}>\frac{x}{20}>\frac{5}{11}\)

\(\Leftrightarrow\frac{605}{220}>\frac{11x}{220}>\frac{100}{220}\)

\(\Leftrightarrow\frac{55}{20}>\frac{x}{20}>\frac{9,\left(09\right)}{20}\)

\(\Rightarrow x\in\left\{11;22;33;44\right\}\)

Ta quy đồng mẫu số:

\(\frac{11}{4}\)>\(\frac{x}{20}\)>\(\frac{5}{11}\)

-> \(\frac{11.20.11}{4.20.11}\) >  \(\frac{x.11.4}{4.20.11}\)>   \(\frac{5.4.20}{4.20.11}\)

-> \(\frac{2420}{880}\)>   \(\frac{44x}{880}\)>    \(\frac{400}{880}\)

-> 2420  >  44x  >  400

-> 44x thuộc {401;...;2419}

-> x thuộc {10;11;12;13;...;51;52;53;54}

\(C=5\frac{9}{10}:\frac{3}{2}-\left(2\frac{1}{3}.4\frac{1}{2}-2.2\frac{1}{3}\right):\frac{7}{4}\)

\(=\frac{59}{10}:\frac{3}{2}-\left(\frac{7}{3}.\frac{9}{2}-2.\frac{7}{3}\right):\frac{7}{4}\)

\(=\frac{59}{15}-\left[\frac{7}{3}\left(\frac{9}{2}-2\right)\right]:\frac{7}{4}\)

\(=\frac{59}{15}-\frac{35}{6}:\frac{7}{4}\)

\(=\frac{59}{15}-\frac{10}{3}\)

\(=\frac{9}{15}=\frac{3}{5}\)

\(\cdot62,87+35,14+4,13+8,35+4,86+5,65\)

\(=\left(62,87+4,13\right)+\left(35,14+4,86\right)+\left(8,35+5,65\right)\)

\(=67+40+14\)

\(=121\)

\(\frac{2x+3}{5x+2}=\frac{4x+5}{10x+2}\left(DK:x\ne-\frac{2}{5};x\ne-\frac{1}{5}\right)\)

\(\Rightarrow\left(2x+3\right)\left(10x+2\right)=\left(4x+5\right)\left(5x+2\right)\Rightarrow20x^2+34x+6=20x^2+33x+10\Rightarrow x=4\)(thoả mãn)

Vậy x = 4

\(\frac{2x+3}{5x+2}=\frac{4x+5}{10x+2}\)

\(\Leftrightarrow\left(2x+3\right)\left(10x+2\right)=\left(5x+2\right)\left(4x+5\right)\)

\(\Leftrightarrow2x\left(10x+2\right)+3\left(10x+2\right)=5x\left(4x+5\right)\)

\(\Leftrightarrow20x^2+4x+20x+6=20x^2+25x+9x+10\)

\(\Leftrightarrow20x^2+4x+20x+6-\left(20x^2+25x+9x+10\right)=0\)\(\Rightarrow20x^2+24x+6-\left(20x^2+34x+10\right)=0\)

\(\Leftrightarrow-10x-4=0\)

\(\Leftrightarrow-10x=4\)

\(\Leftrightarrow x=-\frac{4}{10}\)

Mình nhầm 

2x+3/5x+2=4x+5/10x+2

=> (2x+3)(10x+2)=(5x+2)(4x+5)

=> 20x^2+4x+30x+6=10x^2+25x+8x+10 ( Vì cả hai vế đều có 10x^2 nên ta xóa đi )

=> 34x+6=33x+10

=> 34x-33x=-6+10

=> x=4

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

2.(5 + x) = 4 - x

10 + 2x = 4 - x

2x + x = 4 - 10

3x = - 6

x = - 2

Bài này nhân chéo đi em ( ĐKXĐ x # 4 )
 10 + 2x = 4 - x
 <=>10 + 2x - 4 + x = 0
<=> 6 + 3x = 0
<=> x = -2

\(\frac{-31}{x}-\frac{7}{25}+\frac{14}{6}=0\)

\(\frac{-31}{x}-\frac{7}{25}=0-\frac{14}{6}\)

\(\frac{-31}{x}=\frac{-14}{6}+\frac{7}{25}\)

\(\frac{-31}{x}=\frac{-154}{75}\)

=> -31 . 75 = -154 . x

     -2325    = -154 . x

      x         = -2325 : ( -154 )

      x         = 15,1 ( rút gọn )

=> \(\frac{7}{3}-\frac{7}{25}=\frac{-31}{x}\)=>\(\frac{175-21}{75}=\frac{-31}{x}\)( Quy đồng bình thường ) 

 => \(\frac{154}{75}=\frac{-31}{x}\)=> ( nhân chéo ) \(154x=-2325\)=> \(x=\frac{-2325}{154}\)Sao mà bạn đăng toàn ra số lẻ vậy =))

\(a)5-\left(x-6\right)=4\left(3-2x\right)\)

\(\Leftrightarrow5-x+6=12-8x\)

\(\Leftrightarrow-x+8x=12-5-6\)

\(\Leftrightarrow7x=1\Leftrightarrow x=\frac{1}{7}\)

a) 5-(x-6)=4(3-2x)

<=>5-x-6=12-8x

<=>-x+8x=2-5-6

<=>7x=1

<=>x=1/7

\(b)3-4x\left(25-2x\right)=8x^2+x-300\)

\(\Leftrightarrow3-100x+8x^2=8x^2+x-300\)

\(\Leftrightarrow101x-303=0\)

\(\Leftrightarrow101\left(x-3\right)=0\)

\(\Leftrightarrow x-3=0\Leftrightarrow x=3\)