This is a good question. From one of the close reasons of questions in Puzzling SE,
This question is off-topic as it appears to be a mathematics problem, as opposed to a mathematical puzzle. For more info, see "Are math-textbook-style problems on topic?" on meta.
What Puzzling SE wants are, in mathematical questions, puzzles not problems/challenges. Here is more information on this. Therefore, this site must do the opposite to avoid overlapping - for example, questions asking to solve a Sudoku wouldn't be allowed. Of course, "math challenges" are acceptable as that is the name of the proposed site.
Please feel free to ask in more detail about this, as it is important to make sure that everything is clarified whilst the proposal is in Definition.