For a certain exam,a score of 86 was 7 standard deviations below…

For a certain exam,a score of 86 was 7 standard deviations below mean and a score of 90 was 3 standard deviations above mean.What was the mean score for 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 #51589