In reality, it probably was not open for debate. This is third grade math, remember. The student probably spent the last three problems working similar question

In reality, it probably was not open for debate. This is third grade math, remember. The student probably spent the last three problems working similar questions covering ratios/fractions. And the student probably spent at least a few weeks of school working similar types of problems on homework. After so long taking these types of classes and tests, if a student answers a question without using knowledge gained from the class and gets the question wrong, well...what did they expect? (Not saying I like it, but it's the way it is many places.)