Class and Level Geekery XI - Can Now Argue Three Times Per Page

[GregTD]

Here are the encounters.

Black Dragon (Possibly gave no xp, and V most likely isn't level 15 yet.)
Xykon(Probably gave no xp)
Divorce Lawyer
Slavers
Purple Wyrm
Finding Girard's message, and escaping the blast.
(Bounty Hunters come. V must be 15 by now. However, V may have been 15 before this.)

Freeing the slaves from the Empire of Blood
The battle with Z, and the battle with the kobold.
Saving Gootrude from a dragon.

Somewhere after the Black Dragon V became 15. Since the Black dragon said V only had 6th and 7th level Spell slots.

So, you who play D&D 3.5: How big of a fight would "Saving Gootrude from a dragon" have to be to, combined with the other, take V from right below 15th level, to 16th level?