Tính biểu thức a) 3/5 + 7/4 − 1 /20

a) \[\frac{3}{5} + \frac{7}{4} - \frac{1}{{20}}\] \[ = \frac{{12}}{{20}} + \frac{{35}}{{20}} - \frac{1}{{20}}\]\[ = \frac{{46}}{{20}} = \frac{{23}}{{10}}\]

b) \[\frac{{13}}{3} - \frac{1}{7} + \frac{7}{{21}}\]\[ = \frac{{91}}{{21}} - \frac{3}{{21}} + \frac{7}{{21}}\] \[ = \frac{{95}}{{21}}\]

c) \[\frac{3}{5} \times \frac{2}{7} + \frac{3}{5} \times \frac{3}{4} + \frac{3}{5}\]

\[ = \frac{3}{5} \times \left( {\frac{2}{7} + \frac{3}{4} + 1} \right)\]

\[ = \frac{3}{5} \times \left( {\frac{8}{{28}} + \frac{{21}}{{28}} + \frac{{28}}{{28}}} \right)\]

\[ = \frac{3}{5} \times \frac{{57}}{{28}}\]

\[ = \frac{{171}}{{140}}\]

d) \[\frac{{154 \times 64}}{{99 \times 24}}\]

\[ = \frac{{14 \times \cancel{{11}} \times \cancel{8} \times 8}}{{9 \times \cancel{{11}} \times \cancel{8} \times 3}}\]

\[ = \frac{{112}}{{27}}\]

e) \[\frac{7}{8}:\frac{1}{2} + \frac{5}{4}:\frac{1}{2} + \frac{{15}}{{16}}:\frac{1}{2}\]

\[ = \frac{7}{8} \times 2 + \frac{5}{4} \times 2 + \frac{{15}}{{16}} \times 2\]

\[ = 2 \times \left( {\frac{7}{8} + \frac{5}{4} + \frac{{15}}{{16}}} \right)\]

\[ = 2 \times \left( {\frac{{14}}{{16}} + \frac{{20}}{{16}} + \frac{{15}}{{16}}} \right)\]

\[ = 2 \times \frac{{49}}{{16}}\]

\[ = \frac{{49}}{8}\]