Answer:
25%
Explanation:
This takes a bit of work but You take your listing price (84) and your discount price(63) and find out how much difference(84-63) there is, in this case there is 21. then you take 84 and multiply it by a percent that you think is reasonable. In this case I started with .15 percent. Finally I got to 25% and I took the number that it made and checked to see if it was the 21 that was the difference of the other two numbers (which it was).