Describe two methods for finding the total price of a bill that includes a 20%

I have two methods, but I am not sure if they are the methods you are looking for.

Let's say the price of the bill is $10, and you need to add a 20% tip.

You can do:

10 · 0.20 = 2

$2 is the tip, so 10 + 2 = 12

your total price is $12.

Another way is:

10 · 1.20 = 12

The "1" in 1.20 keeps the 10, and the ".20" adds the tip.

I think there are other ways to do it but I do not remember, sorry