How can a group of selectors with their rules be named and reused in sass?

Question

Sass

I want to make adaptability with bootstrap like this:

Answer 1

What is shown in your screenshot is done through placeholders . However, judging by the name of your mixin, this is not the final code and you plan to add an @mediaexpression there. In this case placeholder won't work anymore, you will get an error. This option is already implemented through mixins.
Aside note: do not paste the code as a screenshot