Find value of k. Then find the angle measure of the polygon. Sum of angle measures 180°

Aschool typically sells 500 yearbooks each year for 50 dollars each. the economic calls does a project and discovers that they can sell 100 more yearbooks for every $5 decrease in price. the revenue for yearbook sales is equal to the number of yearbooks sold times the price of the yearbook. let x represent the number of $5 decrease in price. if the expression that represents the revenue is written in the form r(x)=(500+ax)(50-bx). to maximize profit, what price should the school charge for the yearbooks? what is the possible maximum revenue? if the school attains the maximum revenue, how many yearbooks will they sell?

Which answer is the solution set to the inequality |x|< 9? a. x< -9 or x> 9 b. x> -9 and x< 9 c. x> -9 or x< 9 d. x< 9 and x< 9

What is the simplified form of (3.25x10^3)(7.8x10^6) written in scientific notation?