b: \(\dfrac{5}{7}-\dfrac{2}{3}\cdot x=\dfrac{4}{5}\)

=>\(\dfrac{2}{3}x=\dfrac{5}{7}-\dfrac{4}{5}=\dfrac{25-28}{35}=\dfrac{-3}{35}\)

=>\(x=-\dfrac{3}{35}:\dfrac{2}{3}=\dfrac{-3}{35}\cdot\dfrac{3}{2}=-\dfrac{9}{70}\)
c: \(\dfrac{1}{2}x+\dfrac{3}{5}x=-\dfrac{2}{3}\)

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

=>\(x\cdot\dfrac{5+6}{10}=\dfrac{-2}{3}\)

=>\(x\cdot\dfrac{11}{10}=-\dfrac{2}{3}\)

=>\(x=-\dfrac{2}{3}:\dfrac{11}{10}=-\dfrac{2}{3}\cdot\dfrac{10}{11}=\dfrac{-20}{33}\)

d: \(\dfrac{4}{7}\cdot x-x=-\dfrac{9}{14}\)

=>\(\dfrac{-3}{7}\cdot x=\dfrac{-9}{14}\)

=>\(\dfrac{3}{7}\cdot x=\dfrac{9}{14}\)

=>\(x=\dfrac{9}{14}:\dfrac{3}{7}=\dfrac{9}{14}\cdot\dfrac{7}{3}=\dfrac{3}{2}\)

Câu a) -3 phần 1/2 

Câu a) 2 mũ 2

a: =>-7/2:(4/5-1/2x)=4

=>4/5-1/2x=-7/2:4=-7/8

=>1/2x=4/5+7/8=67/40

=>x=67/20

b: =>5x=5

=>x=1

c: =>x(-2/3-1/3)=-2

=>-x=-2

=>x=2

d: =>-2/3(x+1)=-1/3+1/2=1/6

=>x+1=-1/6:2/3=-1/6*3/2=-3/12=-1/4

=>x=-1/4-1=-5/4

a: Ta có: \(\left|\dfrac{2}{5}-x\right|+\dfrac{1}{2}=3.5\)

\(\Leftrightarrow\left|x-\dfrac{2}{5}\right|=3\)

\(\Leftrightarrow\left[{}\begin{matrix}x-\dfrac{2}{5}=3\\x-\dfrac{2}{5}=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{17}{5}\\x=-\dfrac{13}{5}\end{matrix}\right.\)

b: Ta có: \(\dfrac{21}{5}+3:\left|\dfrac{x}{4}-\dfrac{2}{3}\right|=6\)

\(\Leftrightarrow3:\left|\dfrac{1}{4}x-\dfrac{2}{3}\right|=6-\dfrac{21}{5}=\dfrac{9}{5}\)

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

\(\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{4}x-\dfrac{2}{3}=\dfrac{5}{3}\\\dfrac{1}{4}x-\dfrac{2}{3}=-\dfrac{5}{3}\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}\dfrac{1}{4}x=\dfrac{7}{3}\\\dfrac{1}{4}x=-1\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{28}{3}\\x=-4\end{matrix}\right.\)

a) Ta có: \(\frac{4}{5}+x=\frac{2}{3}\)

hay \(x=\frac{2}{3}-\frac{4}{5}=\frac{10}{15}-\frac{12}{15}=\frac{-2}{15}\)

Vậy: \(x=\frac{-2}{15}\)

b) Ta có: \(\frac{3}{4}-x=\frac{1}{3}\)

hay \(x=\frac{3}{4}-\frac{1}{3}=\frac{9}{12}-\frac{4}{12}=\frac{5}{12}\)

Vậy: \(x=\frac{5}{12}\)

c) Ta có: \(x-\frac{5}{9}=\frac{-2}{3}\)

hay \(x=\frac{-2}{3}+\frac{5}{9}=\frac{-6}{9}+\frac{5}{9}=-\frac{1}{9}\)

Vậy: \(x=\frac{-1}{9}\)

d) Ta có: \(\frac{\left(4,5-2x\right)}{\frac{3}{4}}=1\frac{1}{3}\)

\(\Leftrightarrow\frac{9}{2}-2x=\frac{4}{3}\cdot\frac{3}{4}=1\)

\(\Leftrightarrow2x=\frac{9}{2}-1=\frac{7}{2}\)

hay \(x=\frac{7}{4}\)

Vậy: \(x=\frac{7}{4}\)

i don't know

b: \(\Leftrightarrow\left[{}\begin{matrix}2x-1=3\\2x-1=-3\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-1\end{matrix}\right.\)