Sure, but that doesn't mean plenty of adults couldn't use a well designed refresher. After all, studies have shown[1] that many adults struggle with arithmetic

Sure, but that doesn't mean plenty of adults couldn't use a well designed refresher. After all, studies have shown[1] that many adults struggle with arithmetic of a level also taught in school. [1] This article summarizes some of the findings of one such study and links to further resources https://qz.com/638845/americans-are-spectacularly-bad-at-answering-even-the-most-basic-math-questions/ https://qz.com/638845/americans-are-spectacularly-bad-at-ans...