"¿Cuántos hombres estudian aquí?"
Translation:How many men study here?
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?