Time is calculated from 00 longitude….Greenwich Mean Time.
For places east of GMT we add one hour for each time zone
For places west of GMT we subtract one hour for each time zone.
The earth rotates 3600 in 24 hours hence it rotates 150 every hour and 10 every 4 minutes.
Question: If it is noon at Greenwich Meridian what time is it at a place 750 west.
Ans: 7 am (See below)