ALGEBRA 15 POINTS please help will give 15 points

What is the slope simplify your answer and write it as a proper fraction, improper fraction, or integer

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

In two or more complete sentences, determine the appropriate model for the given data and explain how you made your decision. (1,-1), (2,0.5), (5,1.5), (8,2)