Ethan works in a department store selling clothing. He makes a guaranteed salary of $500 per week, but is paid a commision on top of his base salary equal to 25% of his total sales for the week. How much would Ethan make in a week in which he made $1250 in sales? How much would Ethan make in a week if he made xx dollars in sales?

Total earnings when selling $1250:
Total earnings when selling $x:
need answer fast