Ans: $54$
Let $x$ and $y$ be the number of male guards and female guards in the exhibition centre respectively.
Let $x$ and $y$ be the number of male guards and female guards in the exhibition centre respectively.
$\left\{ \begin{array}{ll}
x+y=132 & \ldots \unicode{x2460}\\
\dfrac{y}{6} -\dfrac{x}{6} = 4 & \ldots \unicode{x2461} \\
\end{array}\right.$
$\unicode{x2460} -6\times \unicode{x2461}$, we have
$\begin{array}{rcl}
2x & = & 108 \\
x & = & 54
\end{array}$
Therefore, there are $54$ male guards in the centre.
