To find the percentage of the price before tax that Noah tipped the delivery person, you need to know the price of his meal before tax and the amount of the tip that he gave. Let's say that the price of Noah's meal before tax was $18, and he gave the delivery person a $2 tip.
In this case, the percentage of the price before tax that Noah tipped the delivery person is $2 / $18 = 11.11%. This means that he tipped the delivery person 11.11% of the price of his meal before tax.