On a dark gray blackboard, many mathematical formulas are written in chalkOn a dark gray blackboard, many mathematical formulas are written in chalk
Do you remember your school years? what color were the desks, chairs, and blackboardDo you remember your school years? What color were the desks, chairs, and blackboard
Lecture with formulas on the blackboard in front of studentsLecture with formulas on the blackboard in front of students
A lot of white men are sitting at a desk in front of the blackboardA lot of white men are sitting at a desk in front of the blackboard
A teacher standing at the blackboard with a textbookA teacher standing at the blackboard with a textbook
An empty school classroom with desks and a blackboardAn empty school classroom with desks and a blackboard