Hello, thank you for taking the time to post your question!
The underlying formula that you want to use to solve this one is
Tax Rate = (Total Price – Original Price) / Original Price x 100
For this scenario that means
Tax Rate = (6296.40 – 5940) / 5940 x 100 = 6%
Meaning that the tax rate where Derrick lives is 6%
I hope that helps you get moving in a better direction on this type of question! Feel free to reach out if you have any additional questions beyond that :)