Keywords
55-60, 55-60 years, adult, alertness, away, black, black hair, blackboard, blue, caucasian, caucasian ethnicity, classroom, education, equipment, ethnicity, five, five people, front, front view, gray, gray hair, hair, hand, hand raised, high, high school student, indoors, instruction, instructor, learn, learning, look, looking, looking away, mathematics, mature, mature adult, mature men, men, pencil, people, person, presentation, projection, projection equipment, projection screen, purestock, raised, rear, rear view, school, screen, script, shadow, shirt, shirt and tie, stand, standing, student, table, teach, teacher, teaching, textbook, tie, unrecognizable, unrecognizable person, view, waist-up, western, western script, years, stock image, images, royalty free photo, stock photos, stock photograph, stock photographs, picture, pictures, graphic, graphics, fine art prints, print, poster, posters, mural, wall murals, 1574r-015100, 1574r 015100, 1574r015100