a, $\dfrac{2}{3}$ + $\dfrac{3}{4}$ + $\dfrac{7}{2}$
= $\dfrac{2}{3}$ + ( $\dfrac{3}{4}$ + $\dfrac{7}{2}$ )
= $\dfrac{2}{3}$ + $\dfrac{17}{4}$
= $\dfrac{59}{12}$
b, $2$ . $\dfrac{1}{3}$( cái này bị sai đề bạn nha ) + $\dfrac{2}{3}$ . ( $\dfrac{-4}{3}$ + $\dfrac{1}{6}$ ) : $\dfrac{5}{6}$
= $\dfrac{2}{3}$ + $\dfrac{2}{3}$ . $\dfrac{-7}{6}$ : $\dfrac{5}{6}$
= $\dfrac{2}{3}$ + $\dfrac{2}{3}$ . ( $\dfrac{-7}{6}$ : $\dfrac{5}{6}$ ) = $\dfrac{2}{3}$ + $\dfrac{2}{3}$ . $\dfrac{-7}{5}$ = $\dfrac{2}{3}$ . ( $1$ + $\dfrac{-7}{5}$ )
= $\dfrac{2}{3}$ . $\dfrac{-2}{5}$ =$\dfrac{-4}{15}$
c, $\dfrac{5}{7}$ . $\dfrac{19}{26}$ + $\dfrac{5}{7}$ . $\dfrac{18}{26}$ - $\dfrac{5}{14}$ . $\dfrac{11}{13}$
= $\dfrac{5}{7}$ . ( $\dfrac{19}{26}$ + $\dfrac{18}{26}$ ) - $\dfrac{5}{14}$ . $\dfrac{11}{13}$
= $\dfrac{5}{7}$ . $\dfrac{27}{26}$ - $\dfrac{5}{14}$ . $\dfrac{11}{13}$
= $\dfrac{5}{7}$ . $\dfrac{27}{26}$ - $\dfrac{5}{7}$ . $\dfrac{1}{2}$ . $\dfrac{11}{13}$
= $\dfrac{5}{7}$ . ( $\dfrac{27}{26}$ - $\dfrac{1}{2}$ . $\dfrac{11}{13}$ ) = $\dfrac{5}{7}$ . ( $\dfrac{27}{26}$ - $\dfrac{11}{26}$ ) = $\dfrac{5}{7}$ . $\dfrac{8}{13}$ = $\dfrac{40}{91}$
# Try _ hard _ together
