weighted average with a range?

Sorry, i don't know the proper term for this.

Anyway, my wife's on a health course, and has had an assignment back, but although she has passed with 72%, she was hoping to be up in the 90%.

One of her shortfalls was analysing the results of her questionnaire, lecturer said she should have taken it further. So I had a look, being a computer programmer, theorectically, I should be able to work it out, but I can't lol.

Anyway, below is a table of the description, the min possible score, and the max possible score, and on the right is the actual score.

How do I calculate the weighted average of these? I know I can't simply add the results, and divide by 8, as it's meaningless with the range being there. If anyone can help, that would be fantastic, as she's always looking to improve, although she can't change her result now lol... or should I say me, as I'm the subject lol.

Age/ Gender___________3 to 11_______ 9
Health/Medical/Genetics_ -2 to 19_______18
Stress_________________0 to 8_________6
Environment____________2 to 13________12
Lifestyle_______________3 to 15_________9
Diet__________________-2 to 12_________10
Fitness________________-2 to 5_________2
Social __________________ 2 to 7________3