Why is it important to be able to convert measurements in this situation and others?

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%.

Why do interests rates on loans to be lower in a weak economy than in a strong one

Last one and the bottom answer choice is y=(x-4)^2+1 you guys!