\(\Leftrightarrow\left(\left(6\frac{3}{7}-\frac{0,75x-2}{0,35}\right).2,8+1,75\right)=0,1175\)

\(\Leftrightarrow\left(\frac{45}{7}-\frac{0,75x-2}{0,35}\right).2,8=-1,6325\)

\(\Leftrightarrow\frac{45}{7}-\frac{0,75x-2}{0,35}=\frac{-653}{1120}\)

\(\Leftrightarrow\frac{0,75x-2}{0,35}=\frac{7853}{1120}\Leftrightarrow x=5,93875\)

\(\left[\left(6\frac{3}{7}-\frac{0,75x-2}{0,35}\right)\cdot2,8+1,75\right]:0,05=235\)

\(\Leftrightarrow\left(6\frac{3}{7}-\frac{0,75x-2}{0,35}\right)\cdot2,8+1,75=11,75\)

\(\Leftrightarrow\left(6\frac{3}{7}-\frac{0,75x-2}{0,35}\right)\cdot2,8=10\)

\(\Leftrightarrow\left(6\frac{3}{7}-\frac{0,75x-2}{0,35}\right)\cdot2,8=10\)

\(\Leftrightarrow6\frac{3}{7}-\frac{0,75x-2}{0,35}=\frac{25}{7}\)

\(\Leftrightarrow\frac{0,75x-2}{0,35}=\frac{20}{7}\)

\(\Leftrightarrow0,75x-2=1\)

\(\Leftrightarrow0,75x=3\)

\(\Leftrightarrow x=4\)

Vậy \(x=4\)

a: Sửa đề: \(\left[\left(6\dfrac{3}{7}-\dfrac{0,75x-2}{0,35}\right)\cdot2.8+1.75\right]\cdot0.05=2.35\)

\(\Leftrightarrow\left(\dfrac{45}{7}-\dfrac{15x-40}{7}\right)\cdot2.8+1,75=47\)

\(\Leftrightarrow\dfrac{45-15x+40}{7}\cdot2,8=45,25\)

\(\Leftrightarrow\dfrac{85-15x}{7}=\dfrac{905}{56}\)

=>8(85-15x)=905

=>680-120x=905

=>120x=-225

hay x=-15/8

b: \(\dfrac{3}{5}-\dfrac{2}{7}< \dfrac{2}{3}x+\dfrac{3}{4}< \dfrac{1}{2}+\dfrac{7}{9}\)

\(\Leftrightarrow\dfrac{11}{35}-\dfrac{3}{4}< \dfrac{2}{3}x< \dfrac{23}{18}-\dfrac{3}{4}\)

\(\Leftrightarrow-\dfrac{61}{140}< \dfrac{2}{3}x< \dfrac{19}{36}\)

\(\Leftrightarrow-\dfrac{183}{280}< x< \dfrac{19}{24}\)

3: \(\left|x-\dfrac{3}{4}\right|-\dfrac{1}{2}=0\)

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

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