Найдите значение выражения: 8-4,2:(2 5/14-1 4/21).

Ответ:

\[8 - 4,2\ :\left( 2\frac{5^{\backslash 3}}{14} - 1\frac{4^{\backslash 2}}{21} \right) =\]

\[= 8 - \frac{42}{10}\ :\left( 2\frac{15}{42} - 1\frac{8}{42} \right) =\]

\[= 8 - \frac{21}{5}\ :1\frac{7}{42} = 8 - \frac{21}{5}\ :1\frac{1}{6} =\]

\[= 8 - \frac{21}{5}\ :\frac{7}{6} = 8 - \frac{21}{5} \cdot \frac{6}{7} =\]

\[= 8 - \frac{18}{5} = 8 - 3,6 = 4,4.\]