Simplified answer:
The number of people who were less than 2 meters tall in a country with a population of 13.1 million, given that 900,000 people were at least 2 meters tall, is 12.2 million.
Step-by-step explanation:
If 900,000 people were at least 2 meters tall, then the number of people who were less than 2 meters tall can be found by subtracting 900,000 from the total population of 13.1 million.
13.1 million - 900,000 = 12.2 million
Therefore, the number of people who were less than 2 meters tall is 12.2 million.