The answer is: The population age 12 or under was 3680.
<h2>Why?</h2>If in 2010 the population of Kignsford was 8000, and by 2014 the population had increased by 15% we need to calculate the total population and then, calculate how many people was age 12 or under.
We must remember that we cannot work with percentage values, so, to make 15% a real number, we need to divide it by 100:
So,
Calculating the population by 2014, we have:
Then, substituting we have:
Now, calculating the population that was age 12 or under, knowing that it was 2/5 of the total population, we have:
So, the population age 12 or under was 3680.
Have a nice day!