I did competitive math in high school and I can confidently say that they are anything but "basic". I definitely can't solve them now (as an adult) and it's likely I never will. The same is true for most people, including people who actually pursued math in college (I didn't). I'm not going to be the next guy who unknowingly challenges a Putnam winner to do these but I will just say that it is unlikely that someone who actually understands the difficulty of these problems would say that they are not hard.

For those following along but without math specific experience: consider whether your average CS professor could solve a top competitive programming question. Not Leetcode hard, Codeforces hard.