Tính hợp lý: -5/13 . 4/11 + -5/13 : 11/7+ 1 5/13

* Hướng dẫn giải

$\frac{-5}{13}.\frac{4}{11}+\frac{-5}{13}:\frac{11}{7}+1\frac{5}{13}$

$$\begin{gathered} =\frac{-5}{13}.\frac{4}{11}+\frac{-5}{13}.\frac{7}{11}+\frac{18}{13} \\ =\frac{-5}{13}.\left(\frac{4}{11}+\frac{7}{11}\right)+\frac{18}{13} \\ =\frac{-5}{13}.\frac{11}{11}+\frac{18}{13} \\ =\frac{-5}{13}+\frac{18}{13} \\ =\frac{-5+18}{13} \\ =\frac{13}{13} \\ =1 \end{gathered}$$