Separable Phrasal Verb (optional)?

[Mushroom27]

Hi! I have a question related to a doubt that came up today when I got my English test on Phrasal Verbs.

So, the following sentence was involved:

'He returned the money to the man who had lost it.'

And I had to replace the verb 'returned' with 'give back'. So I wrote:

'He gave back the money to the man who had lost it.'

After I got the test and noticed that the teacher marked my answer as wrong, I understood it was correct to say 'gave the money back' instead of what I wrote. But then, a similar case came up, on a sentence whose answer was something like 'the firemen put out the fire' - and a friend of mine said 'put the fire out'. Then, I related it to my own mistake. Except this time, my teacher said her answer was correct. Now, that didn't sound right to me.
I googled it, and 'gave back the money', as well as 'gave the money back' seem to be correct, because it appears to be an optionally separable phrasal verb.
Can anyone help me?

[Mister Micawber]

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Both phrasal verbs you mention are indeed separable.
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_________________
Native English teacher at Mister Micawber's

[Mushroom27]

Yes, but is it optional?

[Mister Micawber]

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Yes, that is what 'separable' means.
.
_________________
Native English teacher at Mister Micawber's

[Mushroom27]

Alright, thank you so much for your help!

[Fayek1972]

Hi mister Micawber ,
I do not think u still remember . I am Feak Amrousy from Egypt , I am a teacher of english language here in Egypt . One day . I sent you an e- mail complaining about being all esl job vacancies in Japan in need of just native speakers . You told me it is not fair but it is the case here .
thanks
faek