Let the original price be x . And the stores are offereing 20% discount. It means , we need to pay only 80 percent.
And it is given that the discount prices is 16.80. That is
0.8x = 16.80
Now we need to get rid of 0.8.
And for that, we divide both sides by0.8,
x =21
So the original price is $21 .