I am appalled that many people have answered it step-by-step (for internet points?)
Or for the fun of solving a puzzle. Yeah, that's more likely.
The OP of that question put nontrivial effort into presentation of the problem. Then even added a "bonus puzzle" after getting answers. In the process, the question got over 5000 views.
Other questions by same OP show creativity and high level of engagement with the problems. And by the way, the OP has answered as many questions as s/he asked.
Sharing puzzles for the fun of it is quite different from dumping one's homework (abstractly duplicated many times all over the Internet) onto the site. My only concern with such questions is the frequent lack of attribution: own creation? from a book? from a contest? But I guess the mentioning of father/math teacher as the source of the problem can be taken at face value, as long as we have no evidence to the contrary.