Respuesta :
I'd put a comma in the third example, so - My mother writes for a magazine, and my father edits novels.
The sentence that needs a comma to be correctly punctuated is the third one - My mother writes for a magazine and my father edits novels-
The correct punctuation would be - My mother writes for a magazine, and my father edits novels-
This is a clear example of a compound sentence.
Compound sentences have at least two independent clauses and are linked by a coordinating conjunction, such as: for, and, but, yet, etc. In this case, they are linked by the conjunction AND.
We use a comma before the conjunction that connects the two independent clauses.