When there is noon at G. M .T. meridian people on another place of the Earth are taking their 6 o’clock morning tea. The longitude of the place is

When it is noon (12:00) at the Greenwich meridian (GMT), a place that is 6 hours earlier will read 6:00 AM. The Earth rotates 360° in 24 hours, so it turns 15° of longitude per hour (1° = 4 minutes); therefore each hour of time difference corresponds to 15° of longitude [1]. Six hours × 15°/hour = 90°. Because the local time is earlier than GMT, the place lies west of Greenwich, i.e., at 90° W. This matches standard examples showing locations near 90°W lag GMT by six hours (noon GMT → 6:00 AM local) [2].

Sources

1. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 18: Latitudes and Longitudes > Longitude and Time > p. 243
2. [2] https://weather.ndc.nasa.gov/utc.html