The Correct answer is D.

Explanation

?

Let N equal the population of Norson, and let T equal the entire population of Transitania. Then T-N is the population of the rest of Transitania.

N is 50% of T-N.

, or 2N=T-N.

This gives 3N=T, or?.

So the population of Norson is one third, or?, of the entire population of Transitania.