Ans: $30$
Let $x$ and $y$ be the number of male members and the number of female members respectively.
Let $x$ and $y$ be the number of male members and the number of female members respectively.
$\left\{ \begin{array}{ll}
x+y=180 & \ldots \unicode{x2460} \\
x=y(1 + 40 \%) & \ldots \unicode{x2461}
\end{array} \right.$
Sub. $\unicode{x2461}$ into $\unicode{x2460}$, we have
$\begin{array}{rcl}
y(1+40\%) + y & = & 180 \\
2.4y & = & 180 \\
y & = & 75 \ \ldots \unicode{x2462}
\end{array}$
Sub. $\unicode{x2462}$ into $\unicode{x2461}$, we have
$\begin{array}{rcl}
x & = & 75 \times (1+40\%) \\
x & = & 105
\end{array}$
Therefore, the difference of the number of male members and the number of female members
$\begin{array}{cl}
= & 105 – 75 \\
= & 30
\end{array}$
