Tính giá trị của biểu thức:

a) \(\frac{{85}}{{54}} - \frac{{10}}{{36}} \times \frac{{14}}{5} = \frac{{85}}{{54}} - \frac{7}{9} = \frac{{85}}{{54}} - \frac{{42}}{{54}} = \frac{{43}}{{54}}\)

b) \(5 - \frac{{35}}{{24}}:\frac{7}{8} = 5 - \frac{{35}}{{24}} \times \frac{8}{7} = 5 - \frac{5}{3} = \frac{{15}}{3} - \frac{5}{3} = \frac{{10}}{3}\)

c) \(\frac{5}{{12}} + \frac{{21}}{{50}} \times \frac{{25}}{{27}} = \frac{5}{{12}} + \frac{{21 \times 25}}{{50 \times 27}} = \frac{5}{{12}} + \frac{7}{{18}} = \frac{{15}}{{36}} + \frac{{14}}{{36}} = \frac{{29}}{{36}}\)

d) \(\frac{{15}}{4}:\left( {\frac{3}{4} + \frac{{11}}{7}} \right) = \frac{{15}}{4}:\left( {\frac{{3 \times 7}}{{4 \times 7}} + \frac{{11 \times 4}}{{7 \times 4}}} \right) = \frac{{15}}{4}:\frac{{65}}{{28}} = \frac{{15}}{4} \times \frac{{28}}{{65}} = \frac{{21}}{{13}}\)