OK so I have just smith a Ebony Bow and gave it a fire enchantment plus I have Ebony arrows and am wearing Archery Enchanted gauntlets and amulet. So here are the numbers.

Bow 66 Damage
26 Fire Damage Enchantment
Arrows do 20 Damage
Gauntlets do 30% more damage
Amulet does 25% more

So is this the equation?

((66+20+26) X 1.30) X 1.25 = ?

Just remember that the 66 bow dmg and 20 arrow dmg can be decreased by enemy armor and the fire dmg can be decresed or even negated by fire resistance.