I use \begin{enumerate} to label the equations (more precisely, problems for the assignments). And I found that the line changes if I change \item.
I know that this situation is natural, but I've seen some papers (the picture included will be one example) that they use multiple spaces in one paper. Please teach me the method of doing this.
(And actually, I'm using the template code downloaded from the internet, so I don't know how my codes are translated.)
taskspackage is what you need. See this answer: https://tex.stackexchange.com/a/324740/101651 – CarLaTeX Oct 24 '19 at 05:27