Please help! I need the answers right now!

2-digit numbers less than 91 which are 1 less than a multiple of 10

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?

Having a hard time understanding this question (see attachment).