\[\boxed{\mathbf{11}\mathbf{.}}\]
\[\textbf{а)}\ 3 \cdot 2 = 6\]
\[3 \cdot 4 = 12\]
\[3 \cdot 6 = 18\]
\[3 \cdot 7 = 21\]
\[3 \cdot 9 = 27\]
\[3 \cdot 10 = 30\]
\[\textbf{б)}\ 3 \cdot 4\ :2 = 12\ :2 = 6\]
\[6\ :2 \cdot 9 = 3 \cdot 9 = 27\]
\[3 \cdot 6\ :2 = 18\ :2 = 9\]
\[3 \cdot 5 + 25 = 15 + 25 = 40\]
\[40 - 3 \cdot 3 = 40 - 9 = 31\]
\[36 + 3 \cdot 8 = 36 + 24 = 60\]