\[\boxed{\mathbf{461.}}\]
\[12\ :6 = 2\]
\[18\ :2 = 9\]
\[24\ :3 = 8\]
\[28\ :4 = 7\]
\[12\ :3 = 4\]
\[18\ :9 = 2\]
\[21\ :3 = 7\]
\[40\ :5 = 8\]
\[32\ :4 = 8\]
\[42\ :6 = 7\]
\[56\ :7 = 8\]
\[27\ :9 = 3\]
\[72\ :9 = 8\]
\[80\ :8 = 10\]
\[54\ :6 = 9\]