\[\boxed{\mathbf{13}\mathbf{.}}\]
\[\textbf{б)}\ 2 \cdot 7 - 5 = 14 - 5 = 9\]
\[45 + 2 \cdot 4 = 45 + 8 = 53\]
\[52 - 2 \cdot 9 = 52 - 18 = 34\]
\[12\ :2 + 27 = 6 + 27 = 33\]
\[41 - 14\ :2 = 41 - 7 = 34\]
\[83 - 20\ :2 = 83 - 10 = 73\]