Ta có: \(\left(-\dfrac{3}{4}-\dfrac{2}{5}\right):\dfrac{3}{7}+\left(\dfrac{3}{5}-\dfrac{1}{4}\right):\dfrac{3}{7}\)
\(=\left(\dfrac{-3}{4}-\dfrac{2}{5}\right)\cdot\dfrac{7}{3}+\left(\dfrac{3}{5}-\dfrac{1}{4}\right)\cdot\dfrac{7}{3}\)
\(=\dfrac{7}{3}\left(\dfrac{-3}{4}-\dfrac{2}{5}+\dfrac{3}{5}-\dfrac{1}{4}\right)\)
\(=\dfrac{7}{3}\cdot\left(\dfrac{1}{5}-1\right)\)
\(=\dfrac{7}{3}\cdot\dfrac{-4}{5}=\dfrac{-28}{15}\)
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