What line of longitude forms the other half of the prime meridian

anti-meridian

Explanation:

The prime meridian is the line that separates the world into two hemispheres, the Western and Eastern hemispheres. The opposite longitudinal line of the prime meridian, running through the Pacific Ocean, is called the anti-meridian. This anti-meridian is actually a longitudinal line that is very important, as that is the line that has been established from which every new day starts, thus the time as well. So the anti-meridian is the line that dictates our daily lives, and most of the people are not aware of it, nor do they know even the name of this longitudinal line. Unlike the prime meridian that has longitude of 0 degrees, the anti-meridian has a longitude of 180 degrees. When these two opposite lines are combined, they divided the planet into two equal parts, and they represent one great line that runs across the whole globe in north-south direction.

20: 5

explanation:

about 20% of the world's population lives in   southwest asia, but on less than 5% of the world's   land area.