This is the 17926th most frequent Russian word.
учебной
Educational; related to learning or study.
In this sentence, 'учебной' modifies 'тетрадь', indicating that the notebook is used for educational purposes.
Я взял учебной тетрадь с собой на урок.
I took the workbook with me to the lesson.
Here, 'учебной' describes 'комнате', showing that the room is intended for studying or learning.
В учебной комнате было тихо.
It was quiet in the study room.
'Учебной' in this context characterizes 'задачей', signifying its educational purpose or nature.