Answer:
The number of dollars it costs to rent the beach house for 5 days .
Explanation:
f(x) = 5+350x. The enunciated says that f(x) is the cost in dollars for renting a house for x days, so f(5) is f(x) with x=5, that is, the cost in dollars for renting the house for 5 days. The exercise doesn't ask for the result but I am going to calculate it, there you can see it better.
f(5) = 5+350(5) = 5+1750 = 1755.
So, for 5 people, the cost in dollars for renting will be f(5)= 1755.