Vista de cerca de un profesor caucásico escribiendo en una pizarra negra en un aula de una escuela primaria - Foto e imágenes de stock

Hand with a chalk, mathematical formulas on a board

Panoramic shot of man writing with chalk on blackboard

Male doctor walking through hospital corridor greeting elderly patient in wheelchair with young nurse stabilized tracking gimbal shot

Teacher draw condition of phase synchronism

Woman with white chalk near green board, closeup. Space for text