I usually have about 12 on my laptop at once, depending on what I'm doing, such as modding maps. However, I'm on my phone right now, and I have 58 tabs open - mostly about programming guides, game walkthroughs and of course, anime.
I haven't closed anything on my phone in months don't make me count them. On my computer though I close everything after I'm done so I rarely have more than 5 at once.
I usualy try to have as little tab open as possible. Most of the time I have around 2-3 tabs open and when I am working it quickly gets to 5-10 tabs open.
i tend to have around 6-12 tabs open depending on what i do, sometimes up to 16 if i'm working on a ton of shit or happen to get obsessive about researching topics that catch my interest.