a, \(\dfrac{4}{5}\) + \(\dfrac{9}{15}\) : \(\dfrac{1}{15}\)
= \(\dfrac{4}{5}\) + \(\dfrac{9}{15}\) \(\times\) 15
= \(\dfrac{4}{5}\)+ 9
= \(\dfrac{4}{5}+\dfrac{45}{5}\)
= \(\dfrac{49}{5}\)
b, - \(\dfrac{5}{15}\) \(\times\) ( 1\(\dfrac{1}{2}\) - (-\(\dfrac{2}{7}\)) - (- \(\dfrac{14}{8}\)) - 1\(\dfrac{1}{3}\)
= - \(\dfrac{1}{3}\) \(\times\) ( \(\dfrac{3}{2}\)+\(\dfrac{2}{7}\)+ \(\dfrac{7}{4}\)) - \(\dfrac{4}{3}\)
= - \(\dfrac{1}{3}\) \(\times\) ( \(\dfrac{42}{28}\)+ \(\dfrac{8}{28}\)+ \(\dfrac{49}{28}\)) - \(\dfrac{4}{3}\)
= - \(\dfrac{1}{3}\) \(\times\) \(\dfrac{99}{28}\) - \(\dfrac{4}{3}\)
= - \(\dfrac{99}{84}\) - \(\dfrac{112}{84}\)
= - \(\dfrac{211}{84}\)
