1) \(\dfrac{11}{12}-\left(\dfrac{2}{5}+x\right)=\dfrac{2}{3}\)

\(\Leftrightarrow\dfrac{11}{12}-\dfrac{2}{5}-x=\dfrac{2}{3}\)

\(\Leftrightarrow x=\dfrac{11}{12}-\dfrac{2}{5}-\dfrac{2}{3}\)

\(\Leftrightarrow x=-\dfrac{3}{20}\)

2) \(2x\left(x-\dfrac{1}{7}\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}2x=0\\x-\dfrac{1}{7}=0\end{matrix}\right.\)\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=\dfrac{1}{7}\end{matrix}\right.\)

3) \(\dfrac{3}{4}+\dfrac{1}{4}:x=\dfrac{2}{5}\)

\(\Leftrightarrow\dfrac{1}{4x}=\dfrac{2}{5}-\dfrac{3}{4}\)

\(\Leftrightarrow\dfrac{1}{4x}=-\dfrac{7}{20}\)

\(\Leftrightarrow4x=-\dfrac{20}{7}\)

\(\Leftrightarrow x=-\dfrac{5}{7}\)

Bài 1:

a: \(x=\dfrac{2}{3}:\dfrac{3}{5}=\dfrac{2}{3}\cdot\dfrac{5}{3}=\dfrac{10}{9}\)

b: \(x=\dfrac{17}{8}:\dfrac{7}{17}=\dfrac{17}{8}\cdot\dfrac{17}{7}=\dfrac{289}{56}\)

c: \(x=-\dfrac{3}{4}:\dfrac{7}{12}=\dfrac{-3}{4}\cdot\dfrac{12}{7}=\dfrac{-63}{28}=-\dfrac{9}{4}\)

d: \(\Leftrightarrow x\cdot\dfrac{1}{6}=\dfrac{3}{8}-\dfrac{1}{4}=\dfrac{1}{4}\)

hay \(x=\dfrac{1}{4}:\dfrac{1}{6}=\dfrac{3}{2}\)

e: \(\Leftrightarrow\dfrac{1}{2}:x=-4-\dfrac{1}{3}=-\dfrac{17}{3}\)

hay \(x=-\dfrac{1}{2}:\dfrac{17}{3}=\dfrac{-3}{34}\)

dad

câu 1:

a) 500-(300)-190+(-210)

= 500-300-190-210

= 200 - 210 -190

=-10 - 190

=-200

b) (-3)³ .5+12.(-6)

= -27.5 -72

=-135 - 72

=-207

c) 15.(-19-4)-19.(15-4)

= 15.(-23) - 19.11

=-345 - 209

=-554

câu 2: tìm x thuộc Z

a) 3x-2=3

=> 3x=3/2

=> x=1/2

b) x chia hết cho 5 và -7<x<11

=> x thuộc {-5;0;5;10}

Câu 1: 

a) Ta có: \(500-\left(300\right)-190+\left(-210\right)\)

\(=500-300-190-210\)

\(=\left(500-300\right)-\left(190+210\right)\)

\(=200-400=-200\)

b) Ta có: \(\left(-3\right)^3\cdot5+12\cdot\left(-6\right)\)

\(=\left(-3\right)^3\cdot5-3\cdot4\cdot3\cdot2\)

\(=-5\cdot3^3-3^2\cdot8\)

\(=3^2\cdot\left(-5\cdot3-8\right)\)

\(=9\cdot\left(-15-8\right)=9\cdot\left(-23\right)=-207\)

c) Ta có: \(15\cdot\left(-19-4\right)-19\cdot\left(15-4\right)\)

\(=-15\cdot19-15\cdot4-15\cdot19+19\cdot4\)

\(=-30\cdot19+4\cdot4\)

\(=-2\cdot\left(15\cdot19+2\cdot4\right)\)

\(=-2\cdot\left(285+8\right)=-586\)

Mọi người ơi tk mình đi mình đang bị âm điểm nè !

hahahahaha................................................................hihihihihihihihihihihihahahahahahahahahahihihihiha             đ c m

1. 2/5 + x= 11/12 - 2/5

=> x= 31/60 - 2/5

=> x= 7/60

Vậy x= 7/60

2. 2x(x - 1/7)= 0

TH1: x=0

TH2: x= 0 + 1/7 = 1/7

Vậy x= 0 hoặc 1/7

3. 1/4 : x= 2/5 - 3/4

=> x= 1/4 : (-7/20)

=> x= -5/7

Vậy x= -5/7

1.7/60

2.1/7

3.5/7

a) 11/12-(2/5+x)=2/3

=>2/5+x=11/12-2/3

=>2/5+x=1/4

=>x=1/4-2/5

=>x=-3/20

b) 2.x(x-1,7)=0

=>x(x-1,7)=0

=>x= 0 hoặc x-1,7=0

=>x=0 hoặc x= 1,7

3/4+1/4:x=2/5

=>1/4:x=2/5-3/4

=>1/4:x=-7/20

=>x=1/4:-7/20

=>x=-5/7

a)\(\frac{11}{12}-\left(\frac{2}{5}+x\right)=\frac{2}{3}\)

<=>\(\frac{11}{12}-\frac{2}{5}-x=\frac{2}{3}\)

<=>\(-x=\frac{2}{3}-\frac{11}{12}+\frac{2}{5}\)

<=>\(-x=\frac{3}{20}\)

<=>\(x=-\frac{3}{20}\)

b)\(2x\left(x-\frac{1}{7}\right)=0\)

<=>2x=0 hoặc \(x-\frac{1}{7}=0\)

<=>x=0 hoặc x=\(\frac{1}{7}\)

c)\(\frac{3}{4}+\frac{1}{4}:x=\frac{2}{5}\)

<=>\(\frac{1}{4}:x=\frac{2}{5}-\frac{3}{4}\)

<=>\(\frac{1}{4}:x=-\frac{7}{20}\)

<=>\(x=\frac{1}{4}:\left(-\frac{7}{20}\right)\)

<=>\(x=-\frac{5}{7}\)

`a)-5/6-x=7/12+[-1]/3`

   `-5/6-x=1/4`

   `x=-5/6-1/4`

   `x=-13/12`

`b)(4,5-2x).(-1 4/7)=11/14`

   `(4,5-2x).(-11/7)=11/14`

    `4,5-2x=11/14:(-11/7)=-0,5`

    `2x=4,5-(-0,5)=5`

    `x=5:2=2,5`

`c)(2/11+1/3)x=(1/7-1/8).56`

   `17/33 x=1/56 .56=1`

      `x=33/17`