Remark
No small wonder (that you are stuck). It is one of those problems that is not really a math problem at all. It is a reading question. What you have to catch is the word altitude. Since that 30500 has no variable associated with it, that number must be an altitude.
That being the case, 500 feet has been added to F(x) to get to g(x)
Answer
F (the top answer)
