How many different ways can the first 12 letters of the alphabet be arranged?

Prove that the value of the expression 7^8–7^7+7^6 is divisible by 43.

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?

Hurry which expression is equivalent to 3√x^5y?