a)\(\dfrac{2}{5}+\dfrac{3}{4}:x=\dfrac{-1}{2}\)
=>\(\dfrac{3}{4}:x=\dfrac{-1}{2}-\dfrac{2}{5}\)
=>\(\dfrac{3}{4}:x=\dfrac{-9}{10}\)
=>\(x=\dfrac{3}{4}:\dfrac{-9}{10}\)
=>\(x=\dfrac{3}{4}.\dfrac{-10}{9}\)
=>\(x=\dfrac{-5}{6}\)
b)\(\dfrac{5}{7}-\dfrac{2}{3}.x=\dfrac{4}{5}\)
=>\(\dfrac{2}{3}.x=\dfrac{5}{7}-\dfrac{4}{5}\)
=>\(\dfrac{2}{3}.x=\dfrac{-3}{35}\)
=>\(x=\dfrac{-3}{35}:\dfrac{2}{3}\)
=>\(x=\dfrac{-3}{35}.\dfrac{3}{2}\)
=>\(x=\dfrac{-9}{70}\)
c)\(\dfrac{1}{2}x+\dfrac{3}{5}x=\dfrac{-2}{3}\)
=>\(x\left(\dfrac{1}{2}+\dfrac{3}{5}\right)=\dfrac{-2}{3}\)
=>\(\dfrac{11}{10}x=\dfrac{-2}{3}\)
=>\(x=\dfrac{-2}{3}:\dfrac{11}{10}\)
=>\(x=\dfrac{-2}{3}.\dfrac{10}{11}\)
=>\(x=\dfrac{-20}{33}\)
d)\(\dfrac{4}{7}x-x=\dfrac{-9}{14}\)
=>\(x\left(\dfrac{4}{7}-1\right)=\dfrac{-9}{14}\)
=>\(\dfrac{-3}{7}x=\dfrac{-9}{14}\)
=>\(x=\dfrac{-9}{14}:\dfrac{-3}{7}\)
=>\(x=\dfrac{-9}{14}.\dfrac{-7}{3}\)
=>\(x=\dfrac{3}{2}\)
