\(1,\dfrac{3}{7}+\left(-\dfrac{5}{2}\right)+\left(-\dfrac{3}{5}\right)\)
\(=\dfrac{3}{7}-\dfrac{5}{2}-\dfrac{3}{5}\)
\(=\dfrac{30}{70}-\dfrac{175}{70}-\dfrac{42}{70}\)
\(=\dfrac{-187}{70}\)
\(2,\left(-\dfrac{4}{3}\right)+\left(-\dfrac{2}{5}\right)+\left(-\dfrac{3}{2}\right)\)
\(=\dfrac{-4}{3}-\dfrac{2}{5}-\dfrac{3}{2}\)
\(=\dfrac{-40}{30}-\dfrac{12}{30}-\dfrac{45}{30}\)
\(=\dfrac{-97}{30}\)
\(3,\dfrac{4}{5}-\left(-\dfrac{2}{7}\right)-\dfrac{7}{10}\)
\(=\dfrac{4}{5}+\dfrac{2}{7}-\dfrac{7}{10}\)
\(=\dfrac{56}{70}+\dfrac{20}{70}-\dfrac{49}{70}\)
\(=\dfrac{27}{70}\)
\(4,\dfrac{2}{3}-\left[\left(-\dfrac{7}{4}\right)-\left(\dfrac{1}{2}+\dfrac{3}{8}\right)\right]\)
\(=\dfrac{2}{3}-\left[\dfrac{-7}{4}-\left(\dfrac{4}{8}+\dfrac{3}{8}\right)\right]\)
\(=\dfrac{2}{3}-\left[\dfrac{-7}{4}-\dfrac{7}{8}\right]\)
\(=\dfrac{2}{3}-\left[\dfrac{-14}{8}-\dfrac{7}{8}\right]\)
\(=\dfrac{2}{3}-\dfrac{-21}{8}\)
\(=\dfrac{16}{24}-\dfrac{-63}{24}\)
\(=\dfrac{79}{24}\)
