Calculating a score based on a drop down field value
When working with a dropdown in Twig, it's important to remember that you're dealing with an object (not a simple string).

This is an object:
{{ entry.myDropdown }}


It's easy to forget, however, because Craft works a little magic behind the scenes. There are many objects (including this one) which have an internal __toString behavior. This is called a "magic method", because it will automatically convert the value to a string when you use it as a string.

But in your case, you're not directly outputting it as a string. You're trying to do math with the object, and the object isn't really sure how to respond to that. So nothing gets converted, and your object remains mathematically useless.

Instead, you'll need to append .value to your object. This will give you the selected value of your dropdown, in a format that you can use.

This is the dropdown's selected value:
{{ entry.myDropdown.value }}