It is my observation that everyone -- yes, everyone -- including students, tutors, teachers, web site managers, textbook authors [and this problem's author (see "son" rather than "son's" and "numbers ... is") and me] make errors. Thus, various spelling and grammar checking products are very helpful.
How to resolve this:
- be patient and helpful (note: humor and anger are both extreme)
- create a review or IV&V system (see Wikipedia)
- be an excellent example
With this problem statement, I would analyze it to determine whether an answer(s) could be given without raising a complaint. So, there are numbers near "42.71," and these are good numbers to compare; there are numbers in the 50's, so "5.7" is probably some other value, and 0.93 is just an outlier.
Now, how this information is presented to the homework's author will (perhaps unfairly) reflect on the person raising the complaint. This situation extends from family to school to locale to national diplomacy (see disrespect during Obama's China visit).