b) 4/9 . 13/3 - 4/3 . 10/9

* Hướng dẫn giải

$\begin{array}{l}\mathrm{b}) \frac{4}{9}.\frac{13}{3}-\frac{4}{3}.\frac{10}{9}\\ =\frac{4}{9}.\frac{13}{3}-\frac{4}{9}.\frac{10}{3}\\ =\frac{4}{9}\left(\frac{13}{3}-\frac{10}{3}\right)\\ =\frac{4}{9}.\frac{3}{3}=\frac{4}{9}\end{array}$