In order to solve this you would need to take the difference in population and then divide by the difference of the number of years that have passed. So first we figure that there is a 30 million difference in population over the course of 10 years. So you would take 30 and divide by 10. Your problem would then appear as this 30/10=3 ... ( I removed all unnecessary zeros from the equation to simplify it). The answer is an annual rate of 3 million people per year (after adding back all necessary zeros to get back to the proper population number in the millions).