Question

what is the time and day at a certain place on 20 degrees West longitude when it is to a on Thursday at a place 11 degree east longitude​

Answer 1

There are 360 degrees in a circle and 24 hours in a day. Divide 360 by 24 and you get 15. There fore every 15 degrees of longitude equals 1 hour. Moving east is later, and west is earlier. If my arithmetic is correct your question works out to about 7 hours 20 minutes earlier so that's about 9.20 am. However time zones round the minutes off to the nearest hour or sometimes 30 minutes, so you would need to check if this is a real life example rather than a theoretical question.