Ключевые слова: background, black, blackboard, board, business, calculate, chalk, chalkboard, class, classroom, college, complex, complicated, concept, drawing, education, equation, exam, formula, handwriting, high, illustration, inspiration, intelligent, knowledge, learn, lecture, lesson, line, mathematical, pattern, problem, school, science, sign, solution, study, studying, success, symbol, teach, teacher, text, theory, university, white, word, write,