What is -4 1/2 as a decimal?

15 point ! ~ see if you know the answer to both you!

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%.

Icould really use some with this question.