You would normally say that just the same - "¿Cuántos hombres estudian aquí?"
Forming a proper question in English is complicated. In such a question that includes a question word, you only need an auxiliary verb if the thing you ask about is not the subject.
Asking about the subject:
- How many people work here?
- Who slept in my bed?
- What bothers you?
Asking about the object; the subject is marked in italics:
- How many people do you employ?
- Who did John sleep with?
- What do you do?
Study is a full verb so "do" isn't required (like in "do drugs") but it could be inserted if you wanted to emphasize something like the reality of their studies.
I believe a good example of an instance for placing "do" as you have asked would be if there had been a discussion already about whether any men ever studied in that place and could easily include some other word such as: "Well, how many men do study here?"
My answers 'how many men do study here?'. How could it be marked incorrect?
It is not exactly wrong, but it's not the most common way to form this question. Usually, if you ask about the subject, you just use the full verb:
- How many men study here? - "Men" is the subject.
- What do the men study here? - "Men" is the subject; "what" is the direct object.
- Where do the men study? - "Men" is the subject; "where" is an object.
When Duo spots a mistyped word in your sentence, it runs a search through all other words in its database for a word that matches yours exactly. If it finds one, it'll grade your sentence as wrong because you might have deliberately translated it wrong.
Normally when you have a gender mismatch (like writing "*cuántas hombres" here instead of "cuántos hombres"), it'll mark you off, since both cuántas and cuántos are in the database as different words. If it grades it as a typo, that can have two reasons. Either there is no counterpart of the other gender in the database, or the program can't connect to the server to run the search properly.
When I have the wrong answer I need to see my incorrect answer .Many times I'm certain I typed it correctly but am not able to see what I've done wrong !
Sometimes I have a hard time with the womans pronunciation. It's like 80 % the woman's voice. Shouldn't it be more balanced with 50/female 50 male?
Ninos in plural means children or boys. Padres in plural means parents or fathers. Why is people incorrect for hombres? I feel like "How many people study here" is a more natural / typical question than "how many men study here".
Niño can be the gender-neutral "child", padre can be the gender-neutral "parent", but hombre is typically only the male "man".
If you want to ask about people of any gender, you should use persona.