Calculate the location of a place where the local time is noon when it is 7:30 p.m. at Greenwich.

The local time of the place is 12:00 pm.
The GMT is 7:30 pm.
The difference in time is 7:30 hrs or 450 min.
The difference in longitudes will be 112.5° (450/4).
Since the time at given place is less than GMT, the place is to the west of GMT.
So, the longitude of a place where the local time is noon is 112.5° W.