Tính giá trị các biểu thức:

- Hướng dẫn giải

a) $3.\frac{-5}{11}=\frac{3.(-5)}{11}=\frac{-15}{11}$

$\begin{array}{l}b)\frac{3}{5}+\frac{4}{7}.\frac{14}{6}=\frac{3}{5}+\frac{4.14}{7.6}=\frac{3}{5}+\frac{4}{3}\\ \\ c)\frac{10}{21}-\frac{3}{8}.\frac{4}{15}=\frac{10}{21}-\frac{3.4}{8.15}=\frac{10}{21}-\frac{1}{10}\\ \\ d)\left(\frac{2}{3}+\frac{3}{4}\right).\left(\frac{5}{7}+\frac{5}{14}\right)=\left(\frac{8}{12}+\frac{9}{12}\right).\left(\frac{10}{14}+\frac{5}{14}\right)\end{array}$