If you get sentenced to 20 years in prison how much time will you actually serve?

Question

If you get sentenced 20 years in prison, how much time will you actually serve?

Answer 1

In some states 20 years means that you'll be in prison the whole 20 years.

In other states some only serve 50 to 70% of there sentence. 

If the person has the possibility of parole then they could be out in 10 or 15 years.