Ключевые слова: arm, assistance, blackboard, business, businessman, calculate, chalk, charity, classroom, complex, complicated, display, drawing, easel, education, equation, executive, give, hand, help, idea, inspiration, intelligent, knowledge, learn, lecture, lesson, male, man, math, open, palm, person, physics, presentation, profit, reaching, school, science, show, solution, study, suit, support, teach, teacher, theory, university, word, write,