a: \(\dfrac{2}{-9}\cdot\dfrac{7}{15}+\dfrac{-2}{9}\cdot\dfrac{8}{15}+1\dfrac{2}{3}\)
\(=\dfrac{-2}{9}\left(\dfrac{7}{15}+\dfrac{8}{15}\right)+\dfrac{5}{3}\)
\(=-\dfrac{2}{9}+\dfrac{5}{3}=-\dfrac{2}{9}+\dfrac{15}{9}=\dfrac{13}{9}\)
b: \(\dfrac{3}{7}\cdot\dfrac{-9}{13}+\dfrac{3}{7}\cdot\dfrac{-4}{13}+1\dfrac{3}{7}\)
\(=\dfrac{3}{7}\left(-\dfrac{9}{13}+\dfrac{-4}{13}\right)+\dfrac{10}{7}\)
\(=-\dfrac{3}{7}+\dfrac{10}{7}=\dfrac{7}{7}=1\)
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