The price of the item would be $18 which is 20% of the original price. To find this answer you have to first subtract 100% and 80% since 80% is what is being taken off of the total you need to figure out what percentage of the total you are left with. Which comes out to 20% Once I figured that out i set up a ratio where I made 100% and $90 equal, since that is the original price, and made 20% equal to X, since that is what we are trying to find. I the cross multiplied 20 and 90 and got 1800 I took that number and divided by 100 which gave me $18. This is 20% of $90 when the price has been marked down by 80%. I hope that this helps and that it is not to confusing.
