With number 12 and am i right on 13?

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?

Line l passes through points (0,4) and (3,6) what is the slope of a line that is parallel to line l -2/3 -3/2 2/3 3/2

What is the perimeter of a rectangular building that is 80 feet wide and 140 feet deep?