Equations written in chalk on chalkboard.

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Size: 5677px × 4226px
Photo credit: © Andrei Zaripov / Alamy / Afripics
License: Royalty Free
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Keywords: blackboard, board, chalk, chalkboard, class, education, equation, formula, green, law, learning, lecture, lesson, math, mathematics, physical, physics, school, science, scientific, solution, study, theory