What is an equation between x (top) and y(bottom)?

Which equation matches the graph shown ?

Barney & noblet customers can choose to purchase a membership for $25 per year members receive 10% off all store purchases 1. how much would a member pay per year if he bought $50 worth of items each year? 2. write a slope-intercept equation that expresses how much a member pays per year using x to represent his purchases per year 3. how much would a member have to spend per year to pay off his membership fee?

What is the length of the midsegment of a trapezoid with bases of length 15 and 25 ?