I am part of a math club where I have the same number of male colleagues as female colleagues. When a boy is absent, three quarters of the team are girls. Am I a man or a woman? How many women and men are in the club?
Let $H$ and $M$ be the numbers of men and women, respectively, in the club. We have two possibilities: If I am a boy, then $M=H-1$. When one boy is missing, the total number of people in the club is

$$
M+H-1=H-1+H-1=2 H-2
$$

Thus:

$$
M=\frac{3}{4}(2 H-2) \Rightarrow H-1=\frac{3}{4}(2 H-2) \Rightarrow H=1
$$

Therefore, $M=1-1=0$, which is not possible. So I must be a girl, then $M=H+1$ and we have

$$
H+1=\frac{3}{4}(2 H+1-1) \Rightarrow H=2 \text { and } M=3
$$