\[\boxed{\mathbf{1.}}\]
\[1)\ 4 \cdot 9 = 36\]
\[2)\ 7 \cdot 8 = 56\]
\[3)\ 6 \cdot 7 = 42\]
\[4)\ 3 \cdot 8 = 24\]
\[5)\ 5 \cdot 7 = 35\]
\[6)\ 6 \cdot 4 = 24\]
\[7)\ 9 \cdot 6 = 54\]
\[8)\ 7 \cdot 9 = 63\]
\[9)\ 72\ :9 = 8\]
\[10)\ 24\ :3 = 8\]
\[11)\ 48\ :6 = 8\]
\[12)\ 56\ :8 = 7\]
\[13)\ 42\ :6 = 7\]
\[14)\ 40\ :5 = 8\]
\[15)\ 28\ :4 = 7\]
\[\boxed{\mathbf{2.}}\]
\[1)\ 3;\]
\[2)\ 30;\]
\[3)\ 33;\]
\[4)\ 2021\ год;\]
\[5)\ 12.\]
\[\boxed{\mathbf{3.}}\]
\[136,\ 137\]
\[500,\ 501\]
\[999,\ 1000\]
\[1099,\ 1100\]
\[\boxed{\mathbf{4.}}\]
\[68,\ 69\]
\[99,\ 100\]
\[309,\ 310\]
\[5089,\ 5090\]
\[\boxed{\mathbf{5.}}\]
\[Между\ 197\ и\ 203:\]
\[198,\ 199,\ 200,\ 201,\ 202.\]