Count Females in Relationship

Analyzing the expression $a + b - c + d - e \times f$:

• $a + b \implies a$ is female (sister of $b$).
• $b - c \implies b$ is male (brother of $c$).
• $c + d \implies c$ is female (sister of $d$).
• $d - e \implies d$ is male (brother of $e$).
• $e \times f \implies e$ is female (daughter of $f$).
• $f$: gender of $f$ is not specified (could be male or female).

Since the gender of $f$ cannot be determined, the total number of females cannot be determined conclusively.