不等式组应用题求解疑问：无法推导答案解析中的第二个不等式

Hey there! I totally get how confusing those word problems with inequality systems can be—especially when the answer skips steps that feel like they come out of nowhere. Let’s break this down together.

To help you figure out that tricky second inequality (the non-$b+f$ one) and make sense of the whole problem, could you share a few more details:

• The full text of the word problem, including all given conditions and what you’re being asked to solve for
• The complete set of inequalities from the answer解析, with clear labels for what each variable represents (like what $b$ and $f$ stand for)
• Any parts of the解析 that you already follow, so I can focus on the gaps you’re stuck on

Once you share these, I’ll walk you through exactly how that second inequality is derived from the problem’s wording, and make sure the whole logic clicks for you.

内容的提问来源于stack exchange，提问作者user532526