9 miles, you dont even need much math, just common sense. divide 12 by 4 and you get three. multiply 3 by 3 to get 9.
Step-by-step explanation:
Since this circle is partial we will divide the area of the whole circle by 2
the area of a circle is expressed by
so insert 14 for the radius.


divide the area by 2

Hope that helps :)