How do you find and estimate longitude and latitude on a map?

Its just like a graph!

(X,Y)

(Latitude, Longitude)

also, say Sara lives 72, 30 East from the Prime Meridian, and Abby lives 72, 30 West of the Prime Meridian, then they are both an equal distance from the Prime Meridian.  

Now if Sara lived 72, 30 North from the Equator and Abby lived -72, 30 from the Equator, then they would be an equal distance.

due to the fact that it skipped a generation we can tell it is definitely not a dominant trait, therefore it must be recessive. i think this is right let me know!

explanation: