\[\boxed{\mathbf{5.}}\]
\[\textbf{а)}\ 6 \cdot 2 = 12\]
\[6 \cdot 4 = 24\]
\[6 \cdot 3 = 18\]
\[6 \cdot 5 = 30\]
\[\textbf{б)}\ 12\ :2 \cdot 4 = 6 \cdot 4 = 24\]
\[18\ :3 \cdot 5 = 6 \cdot 5 = 30\]
\[36 - 6 \cdot 5 = 36 - 30 = 6\]
\[60 - 6 \cdot 4 = 60 - 24 = 36\]