Para and Por

Is there a rule when to use the word "para" and the word "por"? EXAMPLE Para cuantas las personas? Por cuantos dias? Is there a rule when to use the word "en" and the word "de"? EXAMPLE Porque voy de vacaciones.

Hola erickdh. Bienvenido al foro. In many forums, including this one, it's a good idea to read through some of the other messages before posting a question. The information provided in the thread right before yours (and hence the one you would have seen first had you looked at the Grammar section) should prove helpful in answering your questions. See *__http://spanish.rocketlanguages.com/grammar/help-with-grammar-t1466.html__*.