Tính giá trị biểu thức:

a) \(\frac{5}{{72}}:\frac{3}{8}:\frac{{16}}{9}\)

= \(\frac{5}{{72}} \times \frac{8}{3} \times \frac{9}{{16}}\)

= \(\frac{5}{{27}} \times \frac{9}{{16}}\)

= \(\frac{5}{{48}}\)

b) \(\frac{9}{{14}}:\frac{{18}}{{11}} \times \frac{{20}}{7}:\frac{5}{6}\)

= \(\frac{9}{{14}} \times \frac{{11}}{{18}} \times \frac{{20}}{7} \times \frac{6}{5}\)

= \(\frac{{11}}{{28}} \times \frac{{20}}{7} \times \frac{6}{5}\)

= \(\frac{{55}}{{49}} \times \frac{6}{5}\) = \(\frac{{66}}{{49}}\)