Hi-
First, you'll need to add the score options to the dropdowns, so that the users can select the desired score.
Then you can simply use a formula like this:
/my:myFields/my:HideShowSection_7/my:field146 + /my:myFields/my:HideShowSection_4/my:field147 + /my:myFields/my:HideShowSection_5/my:field148 etc
to get the total score.
I'm not sure what you use in your business to calculate the percentage. If 10 is the highest score, then simply divide the total sum by 10 * number of questions.
Hope this helps!