Answer the following questions:

3. Calculate the time at Durban (longitude 30°E) when the time is 7:00 a.m. at New York (75°W).
5. Calculate the local time at Singapore (104°E) when it is 6:00 p.m. at Greenwich.
 

​​​​​​Dear student,
(3.) When time is 7 A.M in new york, we can calculate the time at GMT which will be 11 A.M. Because for every longitude degree we add 4 minutes. 75 degrees west will be 5 hours ahead the time in GMT. 
Durban is at 30 degrees east of GMT  then using 4 minutes for each degree we get 120 minutes that is 2 hour so it will be 1 P.M in Durban. 

(5) When time is 6 P.M in Greenwich, time in Singapore will be 1 A.M  as it is 105 degrees east of GMT 4 minutes * 105 gives 7 hours ahead of GMT. 

Hope this information clears your doubts.
Regards