\(A=\dfrac{2}{3}+\dfrac{1}{3}.\left(-\dfrac{4}{9}+\dfrac{5}{6}\right):\dfrac{7}{12}\)
\(=\dfrac{2}{3}+\dfrac{1}{3}.\left(\dfrac{-8}{18}+\dfrac{15}{18}\right).\dfrac{12}{7}\)
\(=\dfrac{2}{3}+\dfrac{1}{3}.\dfrac{7}{18}.\dfrac{12}{7}\)
\(=\dfrac{2}{3}+\dfrac{1.1.2}{1.9.1}\)
\(=\dfrac{2}{3}+\dfrac{2}{9}\)
\(=\dfrac{6}{9}+\dfrac{2}{9}\)
\(=\dfrac{8}{9}\)
\(B=\dfrac{3}{7}.\dfrac{2}{9}+\dfrac{4}{7}:\dfrac{9}{2}\)
\(=\dfrac{3}{7}.\dfrac{2}{9}+\dfrac{4}{7}.\dfrac{2}{9}\)
\(=\dfrac{2}{9}.\left(\dfrac{3}{7}+\dfrac{4}{7}\right)\)
\(=\dfrac{2}{9}.\dfrac{7}{7}\)
\(=\dfrac{2}{9}.1\)
\(=\dfrac{2}{9}\)
\(C=\left(\dfrac{5}{7}.0,6-5:3\dfrac{1}{2}\right).\left(40\%-1,4\right).\left(-2\right)^3\)
\(=\left(\dfrac{5}{7}.\dfrac{3}{5}-5:\dfrac{7}{2}\right).\left(\dfrac{40}{100}-\dfrac{7}{5}\right).\left(-8\right)\)
\(=\left(\dfrac{3}{7}-5.\dfrac{2}{7}\right).\left(\dfrac{2}{5}-\dfrac{7}{5}\right).\left(-8\right)\)
\(=\left(\dfrac{3}{7}-\dfrac{10}{7}\right).\left(\dfrac{-5}{5}\right).\left(-8\right)\)
\(=\dfrac{-7}{7}.\left(-1\right).\left(-8\right)\)
\(=\left(-1\right).8\)
\(=-8\)
\(D=4\dfrac{1}{2}:\left(2,5-3\dfrac{3}{4}\right)+\left(-\dfrac{1}{2}\right)^2\)
\(=\dfrac{9}{2}:\left(\dfrac{5}{2}-\dfrac{15}{4}\right)+\dfrac{1}{4}\)
\(=\dfrac{9}{2}:\left(\dfrac{10}{4}-\dfrac{15}{4}\right)+\dfrac{1}{4}\)
\(=\dfrac{9}{2}:\dfrac{-5}{4}+\dfrac{1}{4}\)
\(=\dfrac{9}{2}.\dfrac{-4}{5}+\dfrac{1}{4}\)
\(=\dfrac{-18}{5}+\dfrac{1}{4}\)
\(=\dfrac{-72}{20}+\dfrac{5}{20}\)
\(=\dfrac{-67}{20}\)
\(E=\dfrac{31}{17}+\dfrac{-5}{13}+\dfrac{-8}{13}-\dfrac{14}{17}\)
\(=\left(\dfrac{31}{17}+\dfrac{-14}{17}\right)+\left(\dfrac{-5}{13}+\dfrac{-8}{13}\right)\)
\(=\dfrac{17}{17}+\left(\dfrac{-13}{13}\right)\)
\(=1+\left(-1\right)\)
\(=0\)
\(F=\dfrac{-5}{7}.\dfrac{2}{11}+\dfrac{-5}{7}.\dfrac{9}{11}+\dfrac{5}{7}\)
\(=\dfrac{-5}{7}.\left(\dfrac{2}{11}+\dfrac{9}{11}-1\right)\)
\(=\dfrac{-5}{7}.\left(\dfrac{2}{11}+\dfrac{9}{11}-\dfrac{11}{11}\right)\)
\(=\dfrac{-5}{7}.0\)
\(=0\)
