Tính.

\(\frac{4}{5}\)+ \(\frac{3}{4}\) = \(\frac{{16}}{{20}}\) + \(\frac{{15}}{{20}}\) = \(\frac{{31}}{{20}}\)

\(\frac{{78}}{{42}}\) – \(\frac{4}{7}\) = \(\frac{{13}}{7}\) – \(\frac{4}{7}\)= \(\frac{9}{7}\)

\(\frac{9}{{22}}\) × 33 = \(\frac{{27}}{2}\)

\(\frac{4}{9}\) : \(\frac{5}{3}\) = \(\frac{4}{9}\) × \(\frac{3}{5}\) = \(\frac{4}{{15}}\)