\[\boxed{\mathbf{20.}}\]
\[1)\ 5 \cdot 1 = 5\]
\[5 \cdot 2 = 10\]
\[5 \cdot 3 = 15\]
\[5 \cdot 4 = 20\]
\[5\ :5 = 1\]
\[10\ :5 = 2\]
\[15\ :5 = 3\]
\[20\ :5 = 4\]
\[2)\ 6 \cdot 1 = 6\]
\[6 \cdot 2 = 12\]
\[6 \cdot 3 = 18\]
\[6\ :6 = 1\]
\[12\ :6 = 2\]
\[18\ :6 = 3\]