calculate actual contribution from variances

Because the sales volume contribution variance is the difference between the budget contribution and the standard contribution from the actual sales. So if you are given the budget contribution then you do add the sales volume variance to get the standard contribution (and then afterwards adjust by all the other variances. But if you already know the standard contribution from actual sales, then the sales volume variance is not relevant.

Can an example (like the exam type) be presented please? Thanks

I don't understand what you are asking. I work through examples in my free lectures, we have a free test on each chapter, and you will have plenty of examples to practice in your Revision Kit.