\(\dfrac{2}{5}-\left(\dfrac{1}{10}-x\right)=\left(\dfrac{-2}{5}-\dfrac{1}{2}\right)^2\\ =>\dfrac{2}{5}-\dfrac{1}{10}+x=\left(-\dfrac{9}{10}\right)^2\\ =>\dfrac{3}{10}+x=\dfrac{81}{100}\\ =>x=\dfrac{81}{100}-\dfrac{3}{10}=\dfrac{51}{100}\)

\(F=\dfrac{5}{6}.\dfrac{11}{3}-\dfrac{5}{3}.\dfrac{8}{6}\\ =\dfrac{5}{6}.\dfrac{11}{3}-\dfrac{5}{6}.\dfrac{8}{3}\\ =\dfrac{5}{6}.\left(\dfrac{11}{3}-\dfrac{8}{3}\right)\\ =\dfrac{5}{6}.\dfrac{3}{3}=\dfrac{5}{6}.1=\dfrac{5}{6}\)