Final answer:
The most appropriate domain for the function f(x) = 250 - 25x is all non-negative integers greater than or equal to 10.
Step-by-step explanation:
The most appropriate domain for the function f(x) = 250 - 25x is option D) All non-negative integers greater than or equal to 10.
The function models the amount of money Zach will need to purchase the bike x weeks after he starts saving. Since Zach plans to save $25 a week, the function represents the amount of money needed to purchase the bike after x weeks by subtracting 25 times the number of weeks from 250.
In order for the function to make sense, x should be a non-negative integer, meaning it can't be a negative number or a fraction. Furthermore, since Zach plans to start saving, the number of weeks should be greater than or equal to 0. Since the question states that the function is valid for 0 ≤ x ≤ 20, the most appropriate domain is all non-negative integers greater than or equal to 10, which includes the values of x within this range.