\[\boxed{\mathbf{22.}}\]
\[\textbf{а)}\ 2 \cdot 5 = 10\]
\[2 \cdot 8 = 16\]
\[2 \cdot 10 = 20\]
\[3 \cdot 3 = 9\]
\[3 \cdot 5 = 15\]
\[4 \cdot 3 = 12\]
\[12\ :2 = 6\]
\[8\ :4 = 2\]
\[15\ :3 = 5\]
\[\textbf{б)}\ 6 \cdot 2\ :3 = 12\ :3 = 4\]
\[5 \cdot 4\ :2 = 20\ :2 = 10\]
\[9\ :3 \cdot 6 = 3 \cdot 6 = 18\]