From statement to logic I have a problem with the modelling of the following statement in propositional logic (warning, I translated it from italian):

Martha is not a singer, and she doesn't play violin or flute, but not the cello

The exercise ask to use the following simple propositions to model the above:
P = Martha is a singer
Q = Martha plays the violin
R = Martha plays the flute
Z = Martha plays the cello
My solution is 
$$
\neg P \wedge (\neg Q \vee \neg R) \wedge \neg Z
$$
The proposed solution, instead, is
$$
\neg P \wedge \neg (Q \vee R) \wedge \neg Z
$$
I can't understand why, can somebody help me?
EDIT: I'll write the original italian sentence, for those who might be able to give a more accurate translation:

Marta non è una cantante, e non suona o il violino o il flauto, ma non il violoncello

 A: As mentioned in the comment, the translation here is indeed crucial. The use of 'but' does not seem to fit in there (but I have to say that I'm also not a native English speaker). 
In any case, spoken languages can hardly cover the subtleties of logic (except for Lojban...). There are several interpretations or conventions for natural languages that are not applicable for logic. The famous example is
Q: "Do you want coffee or tea?"A: "Yes"
This answer is perfectly valid from a logical point of view. 
In this case, one could try to tanslate the logical statements back into the natural language, and see whether they still say the same as the original sentence, but it's difficult for the aforementioned reasons. When inserting brackets to emphasize the difference, the first statement could be translated as

Martha is not a singer, and she does (not play violin or not play flute), and not play cello

The second one could be 

Martha is not a singer, and she does not (play violin or play flute), and not play cello

So imagine the facts that are given are


*

*Martha is not a singer

*Martha does play violin

*Martha does not play the flute

*Martha does not play cello 


Then the first solution would be true, because the part saying 

... she does (not play violin or not play flute)

is fulfilled, because she does ... not play the flute. 
Maybe when you insert the original (untranslated, Italian) sentence, someone can give you the most appropriate translation.
