Ключевые слова: 50s, 60s, adult, assignment, blackboard, blue, board, book, caucasian, chalk, class, classroom, college, discussing, education, equation, exam, explain, explaining, explanation, eyeglasses, friendly, glasses, happiness, hispanic, knowledge, lecture, lesson, male, man, math, mathematics, people, person, professional, professor, school, standing, student, study, teach, teacher, tie, tutor, university, white, woman, work, writing, young,