Should I use the definite article referring to a number of specific things whose quantity is given with a cardinal number? Like so:
The twelve survivors of the car accident
You should use the definite article when your number includes all of the available individuals.
For example, suppose that the accident had exactly twelve survivors, and all of the survivors had minor injuries. You could say any of these:
If that the accident had more than twelve survivors, but only twelve survivors had injuries, then you could say either of these: