Ключевые слова: adult, background, beautiful, blackboard, casual, caucasian, chalk, chalkboard, class, classroom, college, confident, development, difficult, education, educational, equation, explain, explaining, female, green, information, instructor, knowledge, learn, lecture, lesson, mathematical, occupation, person, professor, school, science, seminar, smart, speaker, standing, student, study, studying, task, teach, teacher, teaching, university, white, woman, work, young,