Those sales make me wonder

Let's say that the price of an item is $x$ . Then, we can make an equation:

$x(1 - \frac{p}{100})^2 = x(1 - \frac{19}{100})$ , $x$ cancel out and we are left with:

$(1 - \frac{p}{100})^2 = 0.81$ , we take square root from both sides:

$1 - \frac{p}{100} = 0.9$

$- \frac{p}{100} = - 0.1$

$p = \boxed{10}$