a) \(\dfrac{4}{5}\) x ( \(\dfrac{5}{4}\) - \(\dfrac{5}{7}\) )
= \(\dfrac{4}{5}\) x \(\dfrac{5}{4}\) - \(\dfrac{4}{5}\) x \(\dfrac{5}{7}\)
= 1 - \(\dfrac{4}{7}\)
= \(\dfrac{3}{7}\)
b) \(\dfrac{5}{8}\) x \(\dfrac{9}{7}\) + \(\dfrac{5}{8}\) x \(\dfrac{5}{7}\)
= \(\dfrac{5}{8}\) x ( \(\dfrac{9}{7}\) + \(\dfrac{5}{7}\) )
= \(\dfrac{5}{8}\) x 2
\(\dfrac{5}{4}\)