We know that the hourly salary of Chasity is $15.00, and that the total amount she earns is entirely determined by the hours she works.
So, if she works more hours, she will earn more. This can be described as that the salary is dependent of the hours she works. Which means that the salary Chasity earns in the dinner is a dependent variable, and the amount of hours Chasity works can be classified as an independent variable, as it doesn't depend of anything else.