a) \(\frac{3}{7}-x=\frac{1}{4}-\left(-\frac{3}{-5}\right)\)
\(\Rightarrow\frac{3}{7}-x=\frac{1}{4}-\frac{3}{5}\)
\(\Rightarrow\frac{3}{7}-x=\frac{-7}{20}\)
\(\Rightarrow x=\frac{3}{7}-\left(\frac{-7}{20}\right)=\frac{3}{7}+\frac{7}{20}\)
\(\Rightarrow x=\frac{109}{140}\)
b) \(\frac{-21}{-13x}+\frac{1}{3}=\frac{-2}{-3}\)
\(\Rightarrow\frac{21}{13x}+\frac{1}{3}=\frac{2}{3}\)
\(\Rightarrow\frac{21}{13x}=\frac{2}{3}-\frac{1}{3}=\frac{1}{3}\)
\(\Rightarrow13x=\frac{3.21}{1}=63\Rightarrow x=\frac{63}{13}\)
a.\(\frac{3}{7}-x=\frac{1}{4}-\left(\frac{-3}{-5}\right)\)
\(\frac{3}{7}-x=\frac{1}{4}-\frac{3}{5}\)
\(\frac{3}{7}-x=\frac{-7}{20}\)
\(x=\frac{109}{140}\)
Vậy\(x=\frac{109}{140}\)
b.\(\frac{-21}{-13}x+\frac{1}{3}=\frac{-2}{-3}\)
\(\frac{21}{13}x+\frac{1}{3}=\frac{2}{3}\)
\(\frac{21}{13}x=\frac{1}{3}\)
\(x=\frac{13}{63}\)
Vậy\(x=\frac{13}{63}\)