Lines of latitude and longitude measure position on the Earth’s surface and work like coordinates. The first coordinate represents how far above or below the equator you are, and the second coordinate measures how far from Greenwich Mean Time you are. A plane starts its flight at (20°S,50°W). It is bound for its destination at (42°S,158°W).
–What will be its position halfway through the flight?
The answer is (31 S, 104 W)