What boundaries of time zones correspond?

The boundaries of time zones correspond roughly to lines of longitude

This is why:
The time in each successive time zone is one hour different from the times in neighboring time zones. To establish time zones, Earth's rotation rate of 360 degrees of longitude per day was divided by 24 hours. The result shows that Earth turns 15 degrees of longitude per hour.

Hopefully I helped ^.^ Mark if possible~

The teacher is mostly talking about the distillation of a mixture