a: \(3\dfrac{3}{7}:1\dfrac{5}{7}\)
\(=\dfrac{24}{7}:\dfrac{12}{7}\)
\(=\dfrac{24}{7}\cdot\dfrac{7}{12}=\dfrac{24}{12}=2\)
b: \(\dfrac{2}{3}+\dfrac{-3}{5}=\dfrac{2}{3}-\dfrac{3}{5}\)
\(=\dfrac{10-9}{15}\)
\(=\dfrac{1}{15}\)
c: \(\dfrac{2}{9}-\left(\dfrac{1}{20}+\dfrac{2}{9}\right)\)
\(=\dfrac{2}{9}-\dfrac{1}{20}-\dfrac{2}{9}\)
\(=-\dfrac{1}{20}\)
d: \(\dfrac{11}{23}\cdot\dfrac{12}{17}+\dfrac{11}{23}\cdot\dfrac{5}{17}+\dfrac{12}{23}\)
\(=\dfrac{11}{23}\left(\dfrac{12}{17}+\dfrac{5}{17}\right)+\dfrac{12}{23}\)
\(=\dfrac{11}{23}+\dfrac{12}{23}=\dfrac{23}{23}=1\)
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