The question is incomplete, here is a complete question.
The population in the united states in 2000 was about 281 million people. in 2015, it was 321 million people. from 2000 to 2015, the population increased %.
Answer : The percentage increase in population from 2000 to 2015 is 14.23 %.
Explanation : Given,
Initial population in the united states in 2000 = 281 million
Final population in the united states in 2015 = 321 million
Formula used :

Now put all the given values in this formula, we get:

The percentage increase in population from 2000 to 2015 is 14.2 %.