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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
![](https://rs.olm.vn/images/avt/0.png?1311)
a: =>11(x-3)=6(x-5)
=>11x-33=6x-30
=>5x=3
=>x=3/5
b: =>(4/3-1/4x-5/12)-2x=8/5*5/3=8/3
=>-9/4x+11/12=8/3
=>-9/4x=32/12-11/12=21/12=7/4
=>x=-7/9
c: =>1/2x-1/3-2/3x-1=x
=>-1/6x-4/3=x
=>-7/6x=4/3
=>x=-4/3:7/6=-4/3*6/7=-24/21=-8/7
d: =>1-2x-3x+1=7/2
=>-5x=3/2
=>x=-3/10
![](https://rs.olm.vn/images/avt/0.png?1311)
`(5/6 -x+7/12) : ( 11/24 -1/8)=11/36`
`=>(5/6 -x+7/12) : (11/24 - 3/24)=11/36`
`=>(5/6 -x+7/12) : 8=11/36`
`=>5/6 -x+7/12=11/36 xx 8`
`=>5/6 -x+7/12=22/9`
`=> x+7/12=5/6-22/9`
`=> x+7/12=-29/18`
`=>x=-29/18 -7/12`
`=>x=-79/36`
![](https://rs.olm.vn/images/avt/0.png?1311)
d: =>-x-5/6=7/12-4/12=3/12=1/4
=>-x=1/4+5/6=13/12
hay x=-13/12
e: =>x+3=-5
hay x=-8
f: =>4,5-2x=-1/2
=>2x=5
hay x=5/2
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\dfrac{11}{12}x+\dfrac{3}{4}=-\dfrac{1}{6}\)
\(\Leftrightarrow\dfrac{11}{12}x=-\dfrac{1}{6}-\dfrac{3}{4}\)
\(\Leftrightarrow\dfrac{11}{12}x=-\dfrac{11}{12}\)
\(\Leftrightarrow x=-\dfrac{11}{12}:\dfrac{11}{12}\)
\(\Leftrightarrow x=-\dfrac{11}{12}.\dfrac{12}{11}\)
\(\Leftrightarrow x=-1\)
\(b,3-\left(\dfrac{1}{6}-x\right).\dfrac{2}{3}=\dfrac{2}{3}\)
\(\Leftrightarrow3-\dfrac{2}{3}.\left(\dfrac{1}{6}-x\right)=\dfrac{2}{3}\)
\(\Leftrightarrow3-\dfrac{1}{9}+\dfrac{2}{3}x=\dfrac{2}{3}\)
\(\Leftrightarrow\dfrac{2}{3}x=\dfrac{2}{3}-3+\dfrac{1}{9}\)
\(\Leftrightarrow\dfrac{2}{3}x=-\dfrac{20}{9}\)
\(\Leftrightarrow x=-\dfrac{20}{9}:\dfrac{2}{3}\)
\(\Leftrightarrow x=-\dfrac{10}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,\dfrac{x}{10}=\dfrac{-11}{5}\Rightarrow x.5=10.\left(-11\right)=-110\\ \Rightarrow-22\\ b,\dfrac{-6}{x}=\dfrac{30}{60}\Rightarrow-6.60=x.30=-120\\ \Rightarrow x=-4\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) Ta có: \(\dfrac{x}{3}=\dfrac{7}{25}+\dfrac{-1}{5}\)
\(\Leftrightarrow\dfrac{x}{3}=\dfrac{7}{25}+\dfrac{-5}{25}=\dfrac{2}{25}\)
hay \(x=\dfrac{6}{25}\)
Vậy: \(x=\dfrac{6}{25}\)
b) Ta có: \(\dfrac{4}{9}+\dfrac{x}{5}=\dfrac{5}{11}\)
\(\Leftrightarrow\dfrac{x}{5}=\dfrac{5}{11}-\dfrac{4}{9}=\dfrac{45}{99}-\dfrac{44}{99}=\dfrac{1}{99}\)
hay \(x=\dfrac{5}{99}\)
Vậy: \(x=\dfrac{5}{99}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{6:\dfrac{3}{5}-1\dfrac{1}{6}x\dfrac{6}{7}}{\dfrac{4}{5}x\dfrac{10}{11}+5\dfrac{2}{12}}=\left(10-x\right):\left(\dfrac{8}{11}x+\dfrac{31}{6}\right)\)
\(\dfrac{10-\dfrac{7}{6}\cdot x\cdot\dfrac{6}{7}}{\dfrac{8}{11}\cdot x+\dfrac{31}{6}}=\dfrac{10-1\cdot x}{\dfrac{8}{11}\cdot x+\dfrac{31}{6}}=\dfrac{10-\dfrac{11}{11}\cdot x}{\dfrac{8}{11}\cdot x+\dfrac{31}{6}}=\dfrac{10-\dfrac{3}{11}\cdot x}{\dfrac{31}{6}}=>10-\dfrac{3}{11}\cdot x=\dfrac{31}{6} =>\dfrac{3}{11}\cdot x=10-\dfrac{31}{6}=\dfrac{29}{6}=>x=\dfrac{29}{6}:\dfrac{3}{11}=\dfrac{319}{18}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 3
\(\dfrac{55}{23}+\dfrac{-22}{23}\le x\le\dfrac{1}{5}-\dfrac{-1}{6}+\dfrac{79}{30}\)
\(=\dfrac{33}{23}\)\(\le x\le\dfrac{90}{30}\)
\(=\dfrac{33}{23}\le x\le3\)
Mà \(x\in Z\) \(\Rightarrow\)\(x=2\)
Có 1 giá trị thỏa mãn
Chọn A
Bài 4
\(\dfrac{-11}{12}< \dfrac{5}{x}< \dfrac{-11}{15}\)
Chọn D
Bài 5
\(M=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{99\cdot100}\)
\(M=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}\)
\(M=1-\dfrac{1}{100}\)
\(M=\dfrac{100}{100}-\dfrac{1}{100}\)
\(M=\dfrac{99}{100}\)
CHọn C
\(\dfrac{11.\left(3-x\right)}{55}=\dfrac{30}{55}\)
\(3-x=\dfrac{30}{11}\)
\(x=3-\dfrac{30}{11}=\dfrac{3}{11}\)