Đáp án:
a, $\dfrac{-17}{30}$-$\dfrac{11}{-15}$+$\dfrac{-7}{12}$
=BCNN(30;15;12)=60
=$\dfrac{-28}{60}$-$\dfrac{-44}{60}$+$\dfrac{-35}{60}$
=$\dfrac{-28+44-35}{60}$
=$\dfrac{-19}{60}$
b,=$\dfrac{-7}{25}$.($\dfrac{11}{8}$+$\dfrac{2}{13}$)-$\dfrac{18}{25}$
=$\dfrac{-7}{25}$.$\dfrac{159}{104}$-$\dfrac{18}{25}$
=$\dfrac{-1113}{2600}$-$\dfrac{18}{25}$
=$\dfrac{-597}{520}$
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