Final answer:
The percent of decrease, before tax, is 20%.
Step-by-step explanation:
To find the percent of decrease, we can use the formula:
Percent decrease = (original price - new price) / original price * 100%
Using the given values, we can calculate the percent decrease:
Percent decrease = ($12.50 - $10.00) / $12.50 * 100% = $2.50 / $12.50 * 100% = 20%.
Therefore, the percent of decrease, before tax, is 20%.