we use "pro" and "pra" only in everyday speech. The correct/formal is "para um" ou "para uma". E.g.: Nós fomos pra festa Nós fomos para a festa Samething for "num" and "numa". The formal way is "em um" and "em uma" E.g. Eles estavam num carro Eles estavam em um carro

"pro" and "pra" is only in everyday speech. "num" and "numa" is accepted in everyday speech and formally.

Oi, meu nome é Marcelo, Do you want to learn portuguese? I want learn english, so...add me on skype and let´s learn!!! my skype is marcelomirmar68 bye bye !

Hi Christine. We can talk english/portuguese 50/50. My skype: brunocriado