a) Ta có : \(\dfrac{2}{3}+\left(\dfrac{5}{7}+\dfrac{-2}{3}\right)=\dfrac{2}{3}+\dfrac{5}{7}+\dfrac{-2}{3}=\left(\dfrac{2}{3}+\dfrac{-2}{3}\right)+\dfrac{5}{7}=0+\dfrac{5}{7}=\dfrac{5}{7}\)
b) Ta có:
\(12\times\left(\dfrac{7}{6}-\dfrac{8}{12}+\dfrac{29}{4}\right)=12\times\dfrac{7}{6}-12\times\dfrac{8}{12}+12\times\dfrac{29}{4}=\dfrac{2\times6\times7}{6}-\dfrac{12\times8}{12}+\dfrac{3\times4\times29}{4}=2.7-8+3.29=93\)
c: \(=\dfrac{-9}{25}\left(\dfrac{53}{3}-\dfrac{23}{3}\right)=\dfrac{-9}{25}\cdot10=\dfrac{-90}{25}=\dfrac{-18}{5}\)
d: \(=\dfrac{-3}{7}\left(\dfrac{15}{13}+\dfrac{11}{13}-1\right)=\dfrac{-3}{7}\cdot1=-\dfrac{3}{7}\)
e: \(=\dfrac{15}{37}-\dfrac{21}{33}+\dfrac{8}{7}+\dfrac{22}{37}+\dfrac{7}{11}=1-1+\dfrac{8}{7}=\dfrac{8}{7}\)
f: \(=\dfrac{7}{5}-\dfrac{23}{13}+\dfrac{3}{4}+\dfrac{3}{5}-\dfrac{3}{4}=2-\dfrac{23}{13}=\dfrac{3}{13}\)
g: \(=\dfrac{5}{13}+\dfrac{8}{13}-\dfrac{20}{41}-\dfrac{21}{41}-\dfrac{5}{7}=\dfrac{-5}{7}\)
