So when you are dealing with percentages, you want to make them into decimals. 10 % as a decimal is 0.10. You just move over your decimal place two times to get a decimal. Next, you need to multiply it by the original cost. $199.99 · 0.10= 19.99. This is the amount you get off of the original cost. So subtract $19.99 from $199.99, and your new price will be $180. Hope this helps you understand better :D
