Ключевые слова: algebra, black, blackboard, blue, book, calculation, celebration, cell, chalk, clip, clothespin, concept, day, design, digit, earth, education, example, food, geometry, hand, happiness, holiday, illustration, ingredient, learning, mathematics, measurement, month, notebook, number, paper, pastry, pencil, pi, poster, ruler, school, science, sign, slice, spring, student, study, symbol, table, text,