a: \(\left(\dfrac{3}{8}+\dfrac{-1}{4}+\dfrac{5}{12}\right):\dfrac{2}{3}\)
\(=\left(\dfrac{9}{24}-\dfrac{6}{24}+\dfrac{10}{24}\right)\cdot\dfrac{3}{2}\)
\(=\dfrac{13}{24}\cdot\dfrac{3}{2}=\dfrac{13}{16}\)
b: \(\dfrac{-5}{7}\cdot\dfrac{2}{11}+\dfrac{-5}{7}\cdot\dfrac{9}{11}+1\dfrac{5}{7}\)
\(=-\dfrac{5}{7}\left(\dfrac{2}{11}+\dfrac{9}{11}\right)+1+\dfrac{5}{7}\)
\(=-\dfrac{5}{7}+1+\dfrac{5}{7}=1\)
c: \(0,25:\left(10,3-9,8\right)-\dfrac{3}{4}\)
\(=0,25:0,5-\dfrac{3}{4}=\dfrac{1}{2}-\dfrac{3}{4}=-\dfrac{1}{4}\)
d: \(\dfrac{-5}{9}\cdot\dfrac{13}{28}+\dfrac{13}{28}\cdot\dfrac{4}{9}\)
\(=\dfrac{13}{28}\left(-\dfrac{5}{9}+\dfrac{4}{9}\right)\)
\(=\dfrac{13}{28}\cdot\dfrac{-1}{9}=\dfrac{-13}{252}\)
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