Answer:
14734 years
Step-by-step explanation
We know the decay rate with time is given by;

Where K = 0.0001216 (radioactive decay constant)
Also we know the number of atoms remaining to decay in proportion to original number of atoms is given by;

Where,

Here we will find
such that 
So we can say;
⇔ 
⇒ 
Taking natural log on both sides. we get

⇒ 


So, the skull is approximately 14734 years old