Tính.

\(\frac{7}{2}\) + \(\frac{9}{{14}}\) = \(\frac{{49}}{{14}}\) + \(\frac{9}{{14}}\) = \(\frac{{58}}{{14}}\) = \(\frac{{29}}{7}\)

\(\frac{{10}}{3}\) – \(\frac{{70}}{{27}}\) = \(\frac{{90}}{{27}}\) – \(\frac{{70}}{{27}}\) = \(\frac{{20}}{{27}}\)

\(\frac{5}{{28}}\) × \(\frac{{77}}{{55}}\) = \(\frac{1}{4}\)

\(\frac{7}{{15}}\) : \(\frac{2}{3}\) = \(\frac{7}{{15}}\) × \(\frac{3}{2}\) = \(\frac{7}{{10}}\)