While viewing the "Review Close Votes" questions with tag pronunciation kept coming (not less than 20, seriously!) and I feel they are "primarily opinion based". A user created the tag and I don't think this is relevant. What do you people say?
I think pronunciation questions are OK... but I'm much more sympathetic towards questions such as "how do you pronounce Čech/Cholesky/Runge-Kutta" over "how do you pronounce $f'(x)$" since the former have objectively correct answers that are quite easy to get wrong if you have been primarily self-taught from written texts, while the latter are more or less opinion-based. But I won't vote to close either one.
I don't think they are opinion-based. There may be more than one correct answer. At the same time, some things are definitely wrong, e.g. $f(x)$ is not read "$f$ on $x$" by any native speaker of English anywhere.
In fact the little words we say when we read mathematical symbols are very hard to look up, and it's nice to have a question and answer site. I have the same problem in French when I talk to students: how do you read out loud something like $$ 2^8 + 16x = 3? $$
Most textbooks treat this quite badly, e.g. they give the analogue of saying in English "2, raised to the eighth power, when added to 16 times x, is equal to 3," which is a correct but overly wordy translation.
These questions may be better suited to ell.stackexchange.com, but, realistically, someone here is more likely to know the correct answer.