# Mehul 's activity

Algebra Level 3

One day, Mehul wrote the integers 1, 2, 3, ... ,19, 20 on a blackboard. Then he erases any arbitrary numbers $a,b$ and replaces them with a new number of value $a+b-1$. And he repeats it for another 18 times.

Show that there is only one number remain. What is the value of that number?

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