You can create the equation 5.56 = 0.80x
Where 5.56 is the price you paid, x is the original price and 0.80 is the 80% discount that was applied to the original price
To solve this you just need to divide both sides of the equation by .80, by doing this the .80 gets dividied by .80, and any number divide by itself is 1. We re dividing by both sides because otherwise ine of the sides wouldnt equal the other and it wouldnt be an equation.
5.56/.80 = .80/.80x
5.56/.80 = x
x = 6.95
The original price was 6.95