Thực hiện phép tính:

a) \(\frac{1}{3} + \frac{2}{5}.\frac{5}{3}\);

 \(\frac{1}{3} + \frac{2}{5}.\frac{5}{3} = \frac{1}{3} + \frac{2}{3} = 1\)

b) \(\frac{2}{7}.\frac{{ - 12}}{5} + \frac{2}{7}.\frac{{ - 2}}{5}\);

 \(\frac{2}{7}.\frac{{ - 12}}{5} + \frac{2}{7}.\frac{{ - 2}}{5} = \frac{2}{7}.\left( {\frac{{ - 12}}{5} + \frac{{ - 2}}{5}} \right) = \frac{2}{7}.\frac{{ - 14}}{5} = \frac{{ - 4}}{5}\)

c)\(\frac{{{2^7}{{.9}^4}}}{{{4^4}{{.3}^9}}}\).

 \(\frac{{{2^7}{{.9}^4}}}{{{4^4}{{.3}^9}}} = \frac{{{2^7}.{{\left( {{3^2}} \right)}^4}}}{{{{\left( {{2^2}} \right)}^4}{{.3}^9}}} = \frac{{{2^7}{{.3}^8}}}{{{2^8}{{.3}^9}}} = \frac{1}{{2.3}} = \frac{1}{6}\)