https://creativecommons.org/publicdomain/zero/1.0/https://www.rawpixel.com/image/3298902Edit ImageSaveSaveEditCropCustom TextEquations written in chalk on a worn-out blackboard. Original public domain image from Wikimedia CommonsMorePublic DomainFree CC0 image for Personal and Business useInfoView CC0 LicenseJPEGSmall JPEG 1200 x 900 px | 300 dpiLarge JPEG 3264 x 2448 px | 300 dpiFree DownloadEquations written in chalk on a worn-out blackboard. Original public domain image from Wikimedia CommonsMore