This is one of those problems that makes more sense with context. The teacher had the students working on “reasonableness”, which is essentially “does the question I’m asking make sense?”. The students were probably instructed to ignore actually trying to solve the problem when presented with one, but instead explain why the question either does or doesn’t make sense.
In this case the student potentially misunderstood the task. The failure on the teacher’s part is wording the question in such a way that it actually has a reasonable solution, and isn’t necessarily an unreasonable question.
It makes more sense when you remove the fractions, but I assume they were working on them.
It’s easier this way: “John ate 4 slices of pizza. Dave ate 5 slices of pizza. John ate more slices of pizza than Dave. How is this possible?”
The answer they’re looking for is: “This is not possible because 5 slices of pizza is more than 4 slices of pizza.”
It’s a really bizarre question, and is poorly worded, but the concept could be really important depending on the age/ability of the student.
It’s like teaching a kid to fact check I guess.