\[\boxed{\ \mathbf{691\ (691)}.\ Еуроки\ - \ ДЗ\ без\ мороки}\]
\[1)\ 42\ :\frac{1}{2} = 42 \cdot 2 = 84\]
\[2)\ 42\ :\frac{1}{5} = 42 \cdot 5 = 210\]
\[3)\ 42\ :\frac{2}{3} = 42 \cdot \frac{3}{2} = 42\ :2 \cdot 3 =\]
\[= 21 \cdot 3 = 63\]
\[4)\ 42\ :\frac{3}{7} = 42 \cdot \frac{7}{3} = 42\ :3 \cdot 7 =\]
\[= 14 \cdot 7 = 98\]
\[5)\ 42\ :\frac{7}{11} = 42 \cdot \frac{11}{7} =\]
\[= 42\ :7 \cdot 11 = 6 \cdot 11 = 66\]
\[6)\ 42\ :\frac{21}{23} = 42 \cdot \frac{23}{21} =\]
\[= 42\ :21 \cdot 23 = 2 \cdot 23 = 46\]
\[\boxed{\mathbf{691}.}\]
\[1)\ 27 = 3 \cdot 3 \cdot 3\]
\[2)\ 56 = 2 \cdot 2 \cdot 2 \cdot 7\]
\[3)\ 98 = 2 \cdot 7 \cdot 7\]
\[4)\ 88 = 2 \cdot 2 \cdot 2 \cdot 11\]