Thực hiện phép tính \(\frac{8}{{65}} \times \frac{3}{{40}} \times 65 \times \frac{4}{7} + \frac{3}{5} \times \frac{{34}}{{56}}\) ta được phân số tối giản là:

\(\begin{array}{l} \frac{8}{{65}} \times \frac{3}{{40}} \times 65 \times \frac{4}{7} + \frac{3}{5} \times \frac{{34}}{{56}}\\ = \frac{8}{{65}} \times \frac{3}{{40}} \times 65 \times \frac{4}{7} + \frac{3}{5} \times \frac{3}{7}\\ = \frac{{8 \times 3 \times 65}}{{65 \times 40}} \times \frac{4}{7} + \frac{3}{5} \times \frac{3}{7}\\ = \frac{3}{5} \times \frac{4}{7} + \frac{3}{5} \times \frac{3}{7}\\ = \frac{3}{5} \times \left( {\frac{4}{7} + \frac{3}{7}} \right)\\ = \frac{3}{5} \times \frac{7}{7} = \frac{3}{5} \end{array}\)