Damage Boosts

Damage Boosts

There are abilities like Dark Aura (Powers up Pokémon's Dark-type moves by 33%) and Adaptability (Increases the Same Type Attack Bonus from x1.5 to x2; +150% to 200%) and items like BlackGlasses & Dread Plate (Increases power of Dark type moves by 20%), and then theres the Same Type Attack Boost. How is the final result figured out? If I had my Yveltal (Whose ability is Dark Aura) hold DarkGlasses, would it's Dark Type moves be boosted by 53% (20% from Darkglasses, plus 33% from Dark Aura ability) + S.T.A.B. Bonus, or would it be the ability's boost first, then the final result of that be boosted by the DarkGlasses after that?
Examples (damage done, not power of move, S.T.A.B. Bonus excluded to shorten) :
Dark Pulse does 200 damage to enemy Pokemon, + 53%, final result 306 damage.
Dark Pulse dose 200 damage to enemy Pokemon, + 33% from Ability = 266, + 20% from Held Item = final result 319 damage.
P.S.: I get my stats and ect. From serebii