How does the Percentage base work?

[Healyurself]

Hi, this has been confusing me for a day and well I got a lot of opinions on the topic. I want to know how the Percentage Increase work.

Heres an Example of what I mean.

Seal of the Pure: Increase the damage done by Righteousness, Vengence and Corruption by 15%
Glyph of Righteousness: Increase the Damage done by Righteousness by 10%
2 Set Bonus of T8: Increase the Damage done by Righteousness, Vengence and Corruption by 10%

So if I had none of these on, then damage of my Seal of Righteousness is its normal value in this case 1.
What I want to know is if I have those 3 examples on does this increase the original damage of Seal of Righteous by 1.35 or is it 1.3915?

In short terms does Percentages such as these go by;
Percentage A + Percentage B = Percentage C
or is it more Percentage A x Percentage B = Percentage AB

Thanks for any confirmantion and sorry if I have confused people in the process. Also this is Help I didn't know if it went here or the Therocrafting part :o

[Bashal]

In most (if not all) cases, those kinds of bonuses are additive, not multiplicative.

So:

Percentage A + Percentage B = Percentage C

Edit: I'm a little unsure if talents are additive with set bonuses though.

[Healyurself]

Edit: What i said was stupid, I was juding and didn't notice the Judgement glyph was playing in, so i stick to melee swings. I am getting the A+B =C way. Although I maybe wrong