21 + (-21) + (-4) please help me out with this question

What is the value of x in the following equation. -x ^3/2 = -27

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?

10x − 5y + 14 = 0 whats the answer pls