Answer: 20% discount
Work Shown:
amount saved = 84-67.20 = 16.80 dollars
Divide this over the original larger price to get 16.80/84 = 0.20 = 20%
Note how 20% of 84 = 0.20*84 = 16.80 to help check the answer.
Or we can say 0.80*84 = 67.20 which also helps confirm the answer.
The 0.80 is from the fact that you save 20% but still have to pay the remaining 80%