\[\boxed{\mathbf{462\ (462).}\mathbf{\ }Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ \left( 2\frac{5}{9} - 1\frac{20}{21} \right)\ :1\frac{8}{49} + 1\frac{8}{9}\ :6 =\]
\[= \left( \frac{23^{\backslash 7}}{9} - \frac{41^{\backslash 3}}{21} \right)\ :\frac{57}{49} + \frac{17}{9} \cdot \frac{1}{6} =\]
\[= \frac{28 + 17}{54} = \frac{45}{54} = \frac{5}{6}\]