I'm not sure how tests in this academy works, but Deborah's a woman used to taking modern math tests, so she probably wrote her intermediate steps in the provided solving space.
Which will look absolutely nothing like the calculations of the other students, because the people in this setting are Bad At Math.
I suppose if her math notation is sufficiently different that the people in this world can't recognize it, and think of it as drawing numbers and lines in weird places, that somehow scribble to the correct answers, that would explain why they can pass it off as cheating. Most of the current symbolic notation for math operations is pretty historically recent, after all.