tính a. 5/9+3/9; b.8/12-1/3;

* Hướng dẫn giải

$$\begin{gathered} a)\frac{5}{9}+\frac{3}{9}=\frac{8}{9} \\ b)\frac{8}{12}-\frac{1}{3}=\frac{2}{3}-\frac{1}{3}=\frac{1}{3} \end{gathered}$$

$c)\frac{4}{7}\times \frac{5}{2}:\frac{5}{14}=\frac{20}{14}\times \frac{14}{5}=\frac{20}{5}=4$