\(C=-\dfrac{7}{10}\cdot\dfrac{4}{13}+-\dfrac{7}{10}\cdot\dfrac{9}{13}+1\dfrac{7}{10}\)
\(=-\dfrac{7}{10}\cdot\left(\dfrac{4}{13}+\dfrac{9}{13}\right)+\dfrac{17}{10}\)
\(=-\dfrac{7}{10}\cdot1+\dfrac{17}{10}\)
\(=-\dfrac{7}{10}+\dfrac{17}{10}\)
\(=1\)
\(D=0,7\cdot2\dfrac{2}{3}\cdot20\cdot0,375\cdot\dfrac{5}{28}\)
\(=\dfrac{7}{10}\cdot\dfrac{8}{3}\cdot20\cdot\dfrac{3}{8}\cdot\dfrac{5}{28}\)
\(=\left(\dfrac{7}{10}\cdot20\right)\cdot\left(\dfrac{8}{3}\cdot\dfrac{3}{8}\right)\cdot\dfrac{5}{28}\)
\(=14\cdot1\cdot\dfrac{5}{14\cdot2}\)
\(=\dfrac{14\cdot5}{14\cdot2}\)
\(=\dfrac{5}{2}\)
\(c,C=\dfrac{-7}{10}.\dfrac{4}{13}+\dfrac{-7}{10}.\dfrac{9}{13}+1\dfrac{7}{10}\\ =\dfrac{-7}{10}.\left(\dfrac{4}{13}+\dfrac{9}{13}\right)+\dfrac{17}{10}\\ =\dfrac{-7}{10}.1+\dfrac{17}{10}\\ =\dfrac{-7}{10}+\dfrac{17}{10}\\ =1\\ d,D=0,7.2\dfrac{2}{3}.20.0,375.\dfrac{5}{28}\\ =14.\dfrac{8}{3}.\dfrac{15}{224}\\ =\dfrac{112}{3}.\dfrac{15}{224}\\ =\dfrac{5}{2}\)
