Đề bài

Tính:

a)$\left[ {{{\left( {\frac{3}{7}} \right)}^4}.{{\left( {\frac{3}{7}} \right)}^5}} \right]:{\left( {\frac{3}{7}} \right)^7};$          

b)$\left[ {{{\left( {\frac{7}{8}} \right)}^5}:{{\left( {\frac{7}{8}} \right)}^4}} \right].\left( {\frac{7}{8}} \right);$

c)$\left[ {{{\left( {0,6} \right)}^3}.{{\left( {0,6} \right)}^8}} \right]:\left[ {{{\left( {0,6} \right)}^7}.{{\left( {0,6} \right)}^2}} \right]$.