a)\(\dfrac{2}{3}+\dfrac{1}{-4}-\dfrac{5}{18}=\dfrac{8}{12}-\dfrac{3}{12}-\dfrac{5}{18}=\dfrac{5}{18}-\dfrac{5}{18}=\dfrac{5}{36}\)
b)\(=\dfrac{5}{8}+\dfrac{3}{4}-\dfrac{9}{8}=\left(\dfrac{5}{8}-\dfrac{9}{8}\right)+\dfrac{3}{4}=--\dfrac{2}{4}+\dfrac{3}{4}=\dfrac{1}{4}\)
c)\(=\dfrac{6}{7}+\dfrac{1}{7}:\left(-\dfrac{21}{28}+\dfrac{24}{28}\right)=\dfrac{6}{7}+\dfrac{1}{7}\times\dfrac{28}{3}=\dfrac{6}{7}+\dfrac{4}{3}=\dfrac{46}{21}\)
e)\(=\dfrac{9}{17}-\dfrac{5}{13}-\dfrac{8}{13}+\dfrac{1}{17}=\left(\dfrac{9}{17}+\dfrac{1}{17}\right)+\left(-\dfrac{5}{13}-\dfrac{8}{13}\right)\)
\(=\dfrac{8}{17}-1=-\dfrac{9}{17}\)
d)\(=\dfrac{1}{4}\cdot\dfrac{1}{2}-75\%=\dfrac{1}{4}\cdot\dfrac{1}{2}-\dfrac{3}{4}=\dfrac{1}{8}-\dfrac{6}{8}=-\dfrac{5}{8}\)
f)\(=\dfrac{7}{12}\cdot\left(\dfrac{9}{14}+\dfrac{3}{14}+\dfrac{1}{14}\right)=\dfrac{7}{12}\cdot\dfrac{13}{14}=\dfrac{13}{24}\)
giải thích :\(\dfrac{-7}{12}\cdot\dfrac{-1}{14}=\dfrac{7}{12}\cdot\dfrac{1}{14}\)
