Can you please explain how i can work through these problems?

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%.

Having a hard time understanding this question (see attachment).

Which of the following is an example of a rational number? a. π b. √ 9 c. √ 8 d. 3.8362319