Here's how to figure out the latitude of a line that's two-thirds of the way from the equator to the South Pole:

* The Earth's Total Latitude: The Earth has a total latitude of 180 degrees (90 degrees north and 90 degrees south).

* Distance from the Equator: Two-thirds of the total latitude is (2/3) * 180 degrees = 120 degrees.

* South Latitude: Since the line is towards the South Pole, this distance is measured in South Latitude.

Therefore, the latitude of the line that is two-thirds of the way from the equator toward the South Pole is 120 degrees South.