Okidoki, I will throw in my two cents, despite thinking that this problem should not create a huge roadblock for anyone.
The question is
I will leave the straight algebra on the side as it has been covered. I will, however, add a tip which helps in most similar problems. Here is comes … when you see a problem with % … immediately look to rely on multiples of 100!
What is the percent discount the customer receives when he gets a rebate of $20 on a purchase of $100 or
What is the discount rate of 20 per 100? Say the sentence and you have the answer! 