Most cases of a cold for adults goes away within a week or 10 days at most.
Some colds can last as long as 14 days depending on how severe the cold is but if the cold is still not going away after 14 days or 2 weeks then you might want to see a doctor to find out what's going on.
Just be sure to stay hydrated, get plenty of rest and take some cold medicine and use a Humidifier or Vaporizer to add moisture to the air and you should be feeling better within a week or 10 days.