Tính bằng cách thuận tiện:

a) \(\frac{3}{4} \times \frac{6}{8} + \frac{4}{8} \times \frac{3}{4}\)

= \(\frac{3}{4} \times (\frac{6}{8} + \frac{4}{8})\)

= \(\frac{3}{4} \times \frac{5}{4}\) = \(\frac{{15}}{{16}}\)

b) \(\frac{5}{6} \times \frac{7}{8} - \frac{7}{8} \times \frac{5}{6}\)

= \(\frac{5}{6} \times (\frac{7}{8} - \frac{7}{8})\)

= \(\frac{5}{6} \times 0\) = 0