Answer:

Explanation:
As per the given problem, Steve starts with $250, and spent $20 a week, the problem mentions nothing about Steve's savings, therefore, one can assume that they didn't save anything. As the problem requests, parameter (
) will be used for the time, and (
) for the savings.
Steve's saving would be equal to his initial value, minus his expense, in essence;

The initial value, minus the amount spend per week multiplied by the week number will equal the savings left.