a) x-\(\dfrac{2}{3}=\dfrac{-5}{12}\)

    x=\(\dfrac{-5}{12}+\dfrac{2}{3}\)

    x=\(\dfrac{-3}{12}\)

b)\(\dfrac{8}{5}:x=\dfrac{-2}{3}\)

         x=\(\dfrac{8}{5}:\left(\dfrac{-2}{3}\right)\)

         x=\(\dfrac{8}{5}.\left(\dfrac{-3}{2}\right)\)

         x=\(\dfrac{-12}{5}\)

c)1-\(\dfrac{3}{7}.x=-\dfrac{2}{7}\)

        \(\dfrac{3}{7}.x=1-\left(-\dfrac{2}{7}\right)\)

         \(\dfrac{3}{7}.x=\dfrac{9}{7}\)

              x=\(\dfrac{9}{7}:\dfrac{3}{7}\)

              x=\(\dfrac{9}{7}.\dfrac{7}{3}\)

              x=3

a)\(\dfrac{-2}{7}+\dfrac{2}{7}:\dfrac{3}{5}\)

=\(\dfrac{-2}{7}+\dfrac{10}{21}\)

=\(\dfrac{4}{21}\)