Ключевые слова: 3, 14, alphabet, appointment, black, board, by hand, calligraphy, centers, chalk, class, concept, council, crete, decimals, education, equivalence, figures, hand, infinite, letter, mathematics, motivation, number, pi, positive, rudiment, school, sentence, sign, source, speculation, successes, symbol, teaching, that, think, white, witty comment, written,