Add/Subtract Quiz Totals on Results Slide

The built-in quiz variables, e.g. Quiz.ScorePoints are read-only and cannot be changed with triggers. See here for info on workarounds.

CareyG521​: As Michael noted, you can't change the built-in quiz variables with triggers. But there is a workaround for your questions.

Multiple-choice questions can be scored by choice. Here's an example of how that looks in Form View:

• For your situation, use a multiple-choice (MC) question with the responses removed from the Focus order and hidden from view. (If you use a standard graded MC, you'll have to cover the response buttons. If you set up a Freeform MC, you can move the buttons off the slide.)
• Each question would have 3 responses: the correct option worth 10 points, another option worth 9 points, plus an option worth 0 points. 
• Put your custom responses on the slide.
• Before the "Submit multiple choice" trigger, use triggers to change the appropriate MC option to Selected, based on whatever method you're using to evaluate the user's response and possible use of a hint..

That will allow the Results slide to properly score the quiz using the built-in variables. 

To get a clearer picture of what I'm talking about, refer to this demo of how to assign partial credit on a multiple-response question. 

You should create a custom number variable (e.g., ScorePoints). On the Results slide, create a trigger that sets the ScorePoints variable equal to the QuizX.ScorePoints variable when the timeline starts on the slide. Then add another trigger that subtracts the Counter variable from ScorePoints when the timeline starts on this slide. Make sure these two triggers execute in the correct order (top to bottom), so the subtraction occurs after the value is copied from QuizX.ScorePoints.

Finally, reference the custom ScorePoints variable instead of the default QuizX.ScorePoints variable when displaying the final result to ensure the correct score is shown.

Keep in mind that the default QuizX.ScorePoints variable will still be reported to the LMS if quiz reporting is enabled. If you are not reporting the score to an LMS, you can fully customize the interaction without relying on the default score variables.

See the attached example.

Thank you for your suggestions, however, without completely re-working the quiz, I couldn't get your ways to work. 

What I did instead was put times on the triggers. I had the Quiz1.ScorePoints convert to AdjustedScore when timeline starts. Then, I set TotalScore to variable AdjustedScore after 1 second (so it would stop reading the Quiz1.ScorePoints number). Then, after 1.5 seconds, I subtracted Counter from TotalScore. I placed %TotalScore% on the screen for viewing in a "Reveal" state under a Normal state, giving the system time to do all those previously listed calculations. When you click to reveal the score, it worked!