I wouldn't fault Common Core. I'd fault the textbook. That little page on counting-up subtraction didn't make sense to me either, so I went to Wikipedia, read t

I wouldn't fault Common Core. I'd fault the textbook. That little page on counting-up subtraction didn't make sense to me either, so I went to Wikipedia, read this shorter snippet[1], and understood it immediately. That textbook's just crappy. [1] https://en.wikipedia.org/wiki/Subtraction#Counting_up https://en.wikipedia.org/wiki/Subtraction#Counting_up