\(x\times\dfrac{2}{5}-\dfrac{3}{10}=\dfrac{3}{10}=>x\times\dfrac{2}{5}=\dfrac{3}{5}=>x=\dfrac{3}{5}:\dfrac{2}{5}=\dfrac{3}{2}\)
\(\dfrac{7}{20}-\dfrac{1}{2}:x=\dfrac{3}{20}=>\dfrac{1}{2}:x=\dfrac{1}{5}=>x=\dfrac{1}{2}:\dfrac{1}{5}=\dfrac{5}{2}\)
\(\dfrac{7}{9}:\left(x-\dfrac{4}{9}\right)=\dfrac{1}{2}=>x-\dfrac{4}{9}=\dfrac{7}{9}:\dfrac{1}{2}=\dfrac{14}{9}=>x=\dfrac{14}{9}+\dfrac{4}{9}=2\)