Someone me with a math question

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?

Idon't get undoing if its pass adding and subtracting so can someone ? x-2 over 5 = 18

Six random samples were taken each year for three years. the table shows the inferred population for each type of fish for each year.