1/2×-7=1/3(×-12) solve

Can someone me out here number 4 plz

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 best approximation for the area of a circle with a radius of 4 m ? use 3.14 to approximate pi