\[\boxed{\mathbf{12.}}\]
\[7 \cdot 2 + 7 = 14 + 7 = 21\]
\[7 \cdot 3 + 7 = 21 + 7 = 28\]
\[7 \cdot 4 + 7 = 28 + 7 = 35\]
\[7 \cdot 5 + 7 = 35 + 7 = 42\]
\[7 \cdot 6 + 7 = 42 + 7 = 49\]
\[7 \cdot 7 + 7 = 49 + 7 = 56\]
\[7 \cdot 8 + 7 = 56 + 7 = 63\]
\[7 \cdot 9 + 7 = 63 + 7 = 70\]