Tính a) 11/30 + 18/35 . (35/54 - 19/18 - 28/48) b) -23/39 . -13/56

* Hướng dẫn giải

a) 

$\begin{array}{l}\frac{11}{30}+\frac{18}{35}.\left(\frac{35}{54}-\frac{49}{18}-\frac{28}{48}\right)\\ =\frac{11}{30}+\left(\frac{18}{35}.\frac{35}{54}-\frac{18}{35}.\frac{49}{18}-\frac{18}{35}.\frac{28}{48}\right)\\ =\frac{11}{30}+\left(\frac{1}{3}-\frac{7}{5}-\frac{3}{10}\right)\\ =\frac{11}{30}+\frac{-41}{30}=-1\end{array}$

b) $\frac{-23}{39}.\frac{-13}{56}.\frac{70}{23}:\frac{125}{75}=\frac{5}{3.4}.\frac{3}{5}=\frac{1}{4}$