A store normally sells a shirt for 45$. They are on sale right now for 15% off. What is the price of the jeans before tax?

First, convert the 15% to a real mathematical number. For percents, this is always done by dividing the 15% by 100%, or 15% / 100% = 0.150.

Second, find out what 15% of $45 is. This is the amount of the sale discount. This is always found by mulitplying 0.150 by the item's cost $45

So for this sale, you'll save $ 6.75 on this item.

This means, the cost of the item to you is

$45 - $ 6.75 = $38.25.