Tính :

* Hướng dẫn giải

$$\begin{gathered} \frac{1}{3}+\frac{5}{12}=\frac{4}{12}+\frac{5}{12}=\frac{9}{12} \\ \frac{9}{12}-\frac{1}{3}=\frac{9}{12}-\frac{4}{12}=\frac{5}{12} \\ \frac{9}{12}-\frac{5}{12}=\frac{4}{12} \\ \frac{5}{12}+\frac{1}{3}=\frac{5}{12}+\frac{4}{12}=\frac{9}{12} \end{gathered}$$