Ratios stacked like this always feel harder than they are, so let's just work it through.
1. Statement 1 tells us that of the 12 people who quit, men to women is 5:1. Split 12 into a 5:1 ratio and you get 10 men, 2 women. So we know 2 women quit. But we don't know how many women were in the company to begin with, so we can't get a final headcount. Not sufficient alone.
2. Statement 2 tells us that of the original 50 people, men to women is 1:1, meaning 25 women started out. But we don't know how many of the people who quit were women, so we can't subtract anything yet. Not sufficient alone either.
3. Put them together and it clicks: 25 women originally, 2 of them were in the group that quit, so 25 - 2 = 23 women remain.
Answer: C, both statements together, neither alone.
The trap here is that both statements look tempting in isolation. Statement 2 especially, because 25 women feels like it's answering the question, until you remember the question asks about the company after the 12 people left. I catch myself doing this constantly, answering the question I wish was being asked instead of the one actually on the page. Read the question stem one more time, slower, before you lock in an answer choice on DS. It's saved me more points than any content review ever did.