\(a,\\ \Leftrightarrow-\dfrac{10}{5}x+\dfrac{1}{5}x=3\\ \Leftrightarrow-\dfrac{9}{5}x=3\\ \Leftrightarrow x=3:\left(-\dfrac{9}{5}\right)=3.\left(-\dfrac{5}{9}\right)=-\dfrac{5}{3}\\ b,\\ \Leftrightarrow\dfrac{8}{5}x-\dfrac{5}{5}x=-\dfrac{9}{10}\\ \Leftrightarrow\dfrac{3}{5}x=-\dfrac{9}{10}\\ \Leftrightarrow x=\left(-\dfrac{9}{10}\right):\dfrac{3}{5}=\left(-\dfrac{9}{10}\right).\dfrac{5}{3}=-\dfrac{3}{2}\\ c,\\ \Leftrightarrow-3x+4x-\dfrac{10}{21}=\dfrac{9}{21}\\ \Leftrightarrow x-\dfrac{10}{21}=\dfrac{9}{21}\\ \Leftrightarrow x=\dfrac{9}{21}+\dfrac{10}{21}=\dfrac{19}{21}\\ d,\\ \Leftrightarrow\dfrac{2}{3}x+\dfrac{1}{3}x+\dfrac{4}{7}=\dfrac{9}{7}\\ \Leftrightarrow x+\dfrac{4}{7}=\dfrac{9}{7}\\ \Leftrightarrow x=\dfrac{9}{7}-\dfrac{4}{7}=\dfrac{5}{7}\)
\(a,-2x+\dfrac{1}{5}x=3\)
\(x\left(-2+\dfrac{1}{5}\right)=3\)
\(x.\left(\dfrac{-10}{5}+\dfrac{1}{5}\right)=3\)
\(x.\dfrac{-9}{5}=3\)
\(x=3:\dfrac{-9}{5}\)
\(x=3.\dfrac{-5}{9}\)
\(x=\dfrac{1.\left(-5\right)}{3}\)
\(x=\dfrac{-5}{3}\)
Vậy \(x=\dfrac{-5}{3}\)
\(b,\dfrac{8}{5}x-x=\dfrac{-9}{10}\)
\(x\left(\dfrac{8}{5}-1\right)=\dfrac{-9}{10}\)
\(x\left(\dfrac{8}{5}-\dfrac{5}{5}\right)=\dfrac{-9}{10}\)
\(x.\dfrac{3}{5}=\dfrac{-9}{10}\)
\(x=\dfrac{-9}{10}:\dfrac{3}{5}\)
\(x=\dfrac{-9}{10}.\dfrac{5}{3}\)
\(x=\dfrac{\left(-3\right).1}{2.1}\)
\(x=\dfrac{-3}{2}\)
Vậy \(x=\dfrac{-3}{2}\)
\(c,-3x+\left(4x-\dfrac{10}{21}\right)=\dfrac{9}{21}\)
\(-3x+4x-\dfrac{10}{21}=\dfrac{9}{21}\)
\(x\left(-3+4\right)=\dfrac{9}{21}+\dfrac{10}{21}\)
\(x=\dfrac{19}{21}\)
Vậy \(x=\dfrac{19}{21}\)
\(d,\dfrac{2}{3}x-\left(-\dfrac{1}{3}x-\dfrac{4}{7}\right)=\dfrac{9}{7}\)
\(\dfrac{2}{3}x+\dfrac{1}{3}x+\dfrac{4}{7}=\dfrac{9}{7}\)
\(x\left(\dfrac{2}{3}+\dfrac{1}{3}\right)=\dfrac{9}{7}-\dfrac{4}{7}\)
\(x.\dfrac{3}{3}=\dfrac{5}{7}\)
\(x=\dfrac{5}{7}\)
Vậy \(x=\dfrac{5}{7}\)
