Ключевые слова: abstract, algebra, background, black, blackboard, board, calculate, calculus, chalk, chalkboard, class, classroom, college, complex, concept, education, equation, exam, figure, formula, geometry, grunge, learn, lesson, line, math, mathematical, mathematics, minus, number, old, pattern, physics, problem, proof, school, science, scratch, scribble, sign, slate, solution, study, symbol, teach, teacher, theory, vintage, white, write,