There is a curriculum that we have to follow with very clear expectations. And the teacher has to test those specific skills, so when the student comes up with something outside of that skill set, they haven’t demonstrated they’ve mastered them.
Maybe it is possible that some teachers are only familiar with their one way to work the problem and don’t really want to deviate off of that process but that is not true for all math teachers.
Some teachers encourage solving math problems in different ways. Students are even asked to explain their reasoning or how they figured it out instead of just following a memorized algorithm. It’s great!
Based on the given data, the pattern is clear, that was the “right” answer. Math teachers hate this