Ключевые слова: 40s, academic, adult, algebra, algebraic, alphabet, black, board, caucasian, chair, chalk, chalkboard, class, classroom, desk, education, educational, equation, formal, formula, geometry, greenboard, hand, high, indoor, knowledge, letter, male, man, math, mathematics, mature, men, occupation, one, people, problem, profession, raised, school, shirt, side, standing, teacher, teaching, tutor, university, writing,