Question

what is the longitude of a place where the local time is 1:15 pm when it is 4:00 am at chicago 88w

Answer 1

When it is 4 AM at Chicago (set to 90°W). GMT is (6hrs ahead) 10 AM.  

From there 1:15 PM is 3¼ hrs ahead (to east),  

3¼ X 15°E  

= 48° 45'E. Answer...........