I have fifteen open as of the time of replying!

29 on my phone currently. It varies, my phone has gone as high as ~600 in the past, but on desktop usually 2-4 on average, never more than 20

3

There are 2 tabs open: tech.lgbt and retrospring :3

One. And it contains your question.

9, but I have two computers and I don't know how many are open on the other computer.

Depends on what you mean by "open". I have about 700 tabs in various tab groups, but the vast majority of them isn't loaded.