The mattress store marks a mattress up 100%. 100% of $225 is 225. We add 225 to 225 and get 510. Therefore, the store sells the mattress for $510 without tax. When Cassie buys the mattress, we have to add 11% tax. We change 11% to 0.11 and multiply that by the selling price (510). We get 56.10, so that is the tax. We add the tax to the selling price and get $566.10. Cassie pays $566.10 for the mattress.
I hope this helped and please mark me as brainliest!
