\[\boxed{\text{1208.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ 0,2a^{- 2}b^{4} \cdot 5a^{3}b^{- 3} =\]
\[= 1 \cdot a^{- 2 + 3}b^{4 + ( - 3)} = ab\]
\[при\ a = - 0,125;\ \ \ \ \ b = 8:\]
\[ab = - 0,125 \cdot 8 = - 1.\]
\[\textbf{б)}\frac{1}{27}a^{- 1}b^{- 5} \cdot 81a^{2}b^{4} =\]
\[= 3a^{- 1 + 2}b^{- 5 + 4} = 3ab^{- 1} = \frac{3a}{b}\]
\[при\ \ a = \frac{1}{7};\ \ b = \frac{1}{14}:\]
\[\frac{3a}{b} = 3 \cdot \frac{1}{7}\ :\frac{1}{14} = \frac{3}{7} \cdot \frac{14}{1} = 6.\]