Can you help on 13 and 15

Which compound inequality could be represented by the graph?

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?

Rewrite the following quadratic functions in intercept or factored form. show your work. f(x) = 3x^2 - 12