Final answer:
On Black Friday, Kat paid a 6.5% tax on her purchase of airpods.
Step-by-step explanation:
To find the percent tax Kat paid, we need to divide the tax amount by the total cost of the purchase and then multiply by 100.
First, subtract the tax amount from the total cost to find the cost of the item without tax. $137.39 - $8.39 = $129.
Next, divide the tax amount by the cost without tax and multiply by 100 to find the percent tax: $8.39 / $129 * 100 = 6.5%.