For this exercise you need to use the following formula:
[tex]PercentageDecrease=\frac{Initial\text{ }Value-Final\text{ }Value}{|Initial\text{ }Value|}\cdot100[/tex]
In this case, you know that the price of the shoes is usually $80 and now it is $76. Then:
[tex]\begin{gathered} Initial\text{ }Value=80 \\ Final\text{ }Value=76 \end{gathered}[/tex]
Therefore, substituting values into the formula and evaluating, you get:
[tex]\begin{gathered} PercentageDecrease=\frac{80-76}{|80|}\cdot100 \\ \\ PercentageDecrease=\frac{4}{80}\cdot100 \\ \\ PercentageDecrease=5 \end{gathered}[/tex]
Hence, the answer is: 5%
