The average of five numbers is 20

The average of five numbers is 20. If one number is excluded, the average becomes 18. The excluded number is?

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 #32083