\[\boxed{\mathbf{27.}}\]
\[\textbf{а)}\ 5 \cdot 6 = 30\]
\[6 \cdot 7 = 42\]
\[4 \cdot 6 = 24\]
\[14\ :2 = 7\]
\[18\ :3 = 6\]
\[25\ :5 = 5\]
\[\textbf{б)}\ 6 \cdot 6 - 20 = 36 - 20 = 16\]
\[2 + 6 \cdot 8 = 2 + 48 = 50\]
\[100 - 6 \cdot 5 = 100 - 30 = 70\]
\[60 - 45\ :5 = 60 - 9 = 51\]
\[24\ :3 + 32 = 8 + 32 = 40\]
\[91 + 36\ :4 = 91 + 9 = 100\]