Ключевые слова: all, background, basic, blue, budget, business, calculate, calculation, calculator, colorful, common, denotation, design, designer, division, education, elementary, essential, everyday, fundamental, illustration, important, knowledge, learn, main, mark, math, mathematical, mathematics, minus, multiply, operation, operator, percent, percentage, plus, root, school, sign, square, standard, study, symbol, teach, template, text, usual, write,