I teach math in the first year of the university on Argentina. I never use mixed fraction, neither for teaching or research, but many times it's teach in high s

I teach math in the first year of the university on Argentina. I never use mixed fraction, neither for teaching or research, but many times it's teach in high school. So I don't remember the details of the conventions, and I'm not sure if they are the in every country/book. I made some tests: Test 1: 1 13 4 --- = ---- 3 3 OK ...................... Test 2: 1 13 -4 --- = - ---- 3 3 OK ...................... Test 3: -1 13 4 ---- = - ---- 3 3 I never saw it and I'd declare it ilegal. Anyway, assuming it's legal I'd expect it to be 11/3 instead of -13/3. ...................... Test 4: -1 13 -4 ---- = - ---- 3 3 Again, I never saw it and I'd declare it ilegal. I think -11/3 is better, but I'm super confused. Anyway, test 3 and test 4 must be different.