ames-
Did you ever wonder why all college level math text books are written by professors?
Supposedly they make up questions and give them to their students for homework. The ones with solutions are included in the next edition and the ones without solutions are thrown out or edited by the student for extra credit.
When I was teaching high school the software I used to type up exams had an option to check most of the questions to see if there was a solution. (It could only check the computational ones not the word problems and I never used that feature so I don’t know how well it worked.)