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.
