Cộng, trừ, nhân, chia số hữu tỉ  

- Hướng dẫn giải

$\begin{array}{l}\frac{0,84-0,64+\frac{4}{9}+\frac{4}{13}}{\frac{7}{9}+\frac{7}{13}-0,2+0,55}=\frac{0,2+\frac{4}{9}+\frac{4}{13}}{\frac{7}{9}+\frac{7}{13}+0,35}\\ =\frac{\frac{4}{20}+\frac{4}{9}+\frac{4}{13}}{\frac{7}{9}+\frac{7}{13}+\frac{7}{20}}\\ =\frac{4\left(\frac{1}{20}+\frac{1}{9}+\frac{1}{13}\right)}{7\left(\frac{1}{20}+\frac{1}{9}+\frac{1}{13}\right)}=\frac{4}{7}\end{array}$