a) \(\dfrac{3}{7}\cdot\left(-\dfrac{2}{9}\right)+\dfrac{3}{7}\cdot\left(-\dfrac{1}{9}\right)+\dfrac{2}{7}\)
\(=\dfrac{3}{7}\cdot\left(-\dfrac{2}{9}+\dfrac{-1}{9}\right)+\dfrac{2}{7}\)
\(=\dfrac{3}{7}\cdot\left(-\dfrac{1}{3}\right)+\dfrac{2}{7}\)
\(=-\dfrac{1}{7}+\dfrac{2}{7}=\dfrac{1}{7}\)
b) \(\left[\left(-\dfrac{4}{5}\right):\dfrac{5}{8}\right]:\dfrac{25}{16}=\left[\left(-\dfrac{4}{5}\right)\cdot\dfrac{8}{5}\right]\cdot\dfrac{16}{25}=-\dfrac{32}{25}\cdot\dfrac{16}{25}=-\dfrac{512}{625}\)
C) \(\dfrac{3}{7}+\dfrac{4}{12}+\left(-0,5\right)+\left(-\dfrac{28}{21}\right)+\dfrac{-6}{21}\)
\(=\dfrac{3}{7}+\dfrac{1}{3}-\dfrac{1}{2}-\dfrac{4}{3}-\dfrac{2}{7}\)
\(=\dfrac{16}{21}-\dfrac{1}{2}-\dfrac{4}{3}-\dfrac{2}{7}\)
\(=\dfrac{11}{42}-\dfrac{4}{3}-\dfrac{2}{7}=-\dfrac{19}{14}\)
D) \(\left(-\dfrac{3}{4}\right):\left(-\dfrac{16}{21}\right):\dfrac{11}{2}=\left(-\dfrac{3}{4}\right)\cdot\left(-\dfrac{21}{16}\right)\cdot\dfrac{2}{11}=\dfrac{63}{63}\cdot\dfrac{2}{11}=\dfrac{63}{352}\)
e) \(\dfrac{3}{5}-\dfrac{2}{5}\cdot\dfrac{5}{8}=\dfrac{3}{5}-\dfrac{10}{40}=\dfrac{24}{40}-\dfrac{10}{40}=\dfrac{14}{40}=\dfrac{7}{20}\)
