In the exam the average was found to be p mark

In the exam the average was found to be p mark. After deducting typographical error the average marks of 120 student reduced from 90 to 70 . Due to this the average came down by 12 marks. What was the number of students who took the exam?

This problem repeats another one in the library (at most with different numbers), so it's left out of browsing.

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #51352