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

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

   x    =\(\dfrac{-5}{12}\)+\(\dfrac{8}{12}\)

   x    =\(\dfrac{3}{12}\)=\(\dfrac{1}{4}\)

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

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

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

       x=\(\dfrac{-24}{10}\)

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

a)(\(\dfrac{-2}{7}\) +\(\dfrac{2}{7}\)):\(\dfrac{3}{5}\)=\(\dfrac{0}{7}\):\(\dfrac{3}{5}\)=0:\(\dfrac{3}{5}\)=0

b)(\(\dfrac{-8}{19}\)+\(\dfrac{27}{19}\))-(\(\dfrac{-4}{21}\)+\(\dfrac{17}{21}\))=\(\dfrac{19}{19}\)-\(\dfrac{13}{21}\)=\(\dfrac{21}{21}\)-\(\dfrac{13}{21}\)=\(\dfrac{8}{21}\)

c)\(\dfrac{6}{5}\).(\(\dfrac{3}{13}\)-\(\dfrac{16}{13}\))=\(\dfrac{6}{5}\).\(\dfrac{-13}{13}\)=\(\dfrac{6}{5}\).(-1)=\(\dfrac{-6}{5}\)

4/3 ; 1/3 ; 4/7 ; 20/3