Remember that when there is no auxiliary verb in an affirmative sentence as in the present simple or past simple, it is normally necessary to place do/does or did before the subject in questions:

I saw Tom about four weeks ago. ~ When did you last see James?
I visit my grandparents once a month. ~ Do you visit them when Tom is with you?

The exception to this rule is when who/what/which is the subject. Compare the following:

Beth phoned her mum last night. ~ Who did Beth phone? ~ She phoned her mum.
Somebody phoned Beth. ~ Who phoned Beth? ~ I've no idea. They didn't leave a message.
Which buses go to Trafalgar Square? ~ The 36 and the 21 go to Trafalgar Square.
Which bus did you take? ~ I took the 36. The 21 wasn't running.

Thus in your example, Bav, some people or how many people is the subject of the sentence, so no inversion is needed in the first question. When it becomes the object of the sentence, as in the second question below, subject-auxiliary verb inversion is required:

I forgot to tell you. Some people are coming for dinner tonight. ~ How many people are coming? How many people have you invited?

questions through intonation

In spoken English, we can sometimes ask questions by using a rising intonation and no subject-verb inversion when we think we have understood something but want to make sure or find it surprising. Tag questions have a similar purpose. Compare the following:

This is your car? I didn't know you were going to buy a new car. Where did you get the money from?
You're coming to lunch tomorrow, aren't you? And Tom is coming with you?

Note that this word order is not possible after question words such as who/what/which.

indirect questions: no subject-verb inversion

In indirect questions we do not put auxiliary verbs before the subject and there is normally no subject-verb inversion. There is no question mark either in indirect questions. Compare the following:

What's the problem? ~I asked her what the problem was.
Have you seen Tony recently? ~She wanted to know if I had seen Tony recently.
When did you last see him? ~She enquired when I last saw / when I had last seen him.
Will he be coming back, do you think? ~She wondered if he would be coming back.

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