Does anybody teach subtraction using complements? I am a high school math teacher, and I only learned of this method as an adult after stumbling onto a YouTube video about it several years ago. For my own personal scratch work, I prefer this method of subtraction, because I think it is cleaner and more uniform than the borrowing method. I wouldn’t dare use this method for any work meant for student viewing, though. Here is the video I referenced. It explains the method pretty well in about the first 1:20. The remaining two minutes or so after is extra information that is also interesting but not crucial for understanding the method.