Mathematical formula

Hello, I need to show the production time on my product and I want to do it with a NOV so that it is later published in the shopping cart.
My question is how should I perform the formula to achieve this:
If the {variable 1} is between 0 and 10 show the result between 2 + 3
If the {variable 1} is between 11 and 20 show the result between 2 + 4
If the {variable 1} is between 21 and 30 show the result between 2 + 7