\[\boxed{\mathbf{1}\mathbf{.71}}\]
\[\textbf{а)}\ 63\ :9 = 7 + 23 = 30\ :6 =\]
\[= 5 \cdot 7 = 35 + 15 = 50\]
\[\textbf{б)}\ 72\ :9 = 8 + 12 = 20 \cdot 5 =\]
\[= 100\ :10 = 10 + 18 = 28\]
\[\textbf{в)}\ 42\ :7 = 6 \cdot 9 = 54 + 6 =\]
\[= 60\ :10 = 6 + 24 = 30\]
\[\textbf{г)}\ 54\ :9 = 6 \cdot 8 = 48 + 2 =\]
\[= 50\ :5 = 10 + 90 = 100\]