\[\boxed{\mathbf{366}\mathbf{.}}\]
\[1)\ 42\ :\frac{3}{7} = 42 \cdot \frac{7}{3} = 14 \cdot 7 = 98\]
\[2)\ 42\ :\frac{7}{11} = 42 \cdot \frac{11}{7} = 6 \cdot 11 =\]
\[= 66\]
\[3)\ 42\ :\frac{21}{23} = 42 \cdot \frac{23}{21} = 2 \cdot 23 =\]
\[= 46\]