Math Help? I can't figure it out..

I have been trying forever to answer this question, and I think it is pretty simple...I just can't remember. I learned it at the beginning of the year.

I don't want the answer, so I just need the formula for this type of question.

Question: Hugo sold his car after one year for _______. He bought it new for _______. What was the rate of depreciation?

My answers to choose from are percent values, how do I get the percent of depreciation?

You divide the difference between purchase and selling price, and then divide by the purchase price.
Then you multiply by 100 to change it to percent