Huge mathematics fan here. The problem here is this test is testing for “Common Core Math” proficiency, not mathematical proficiency. The final answer is mathematically correct and the work shown is mathematically correct. Now of course this leave those of us that learned math differently scratching our heads as to what is the point. Also the argument that “if the teacher has not covered the commutative property…” falls down for me because the work was still correct. For me it would be Much more confusing if I was told this was incorrect, then taught about the commutative property, and Then told it was correct, because at some point that is going to happen… Right?