Answer:
I want to say <u>Substitution</u>.
Explanation:
They removed the number 5, and inserted an A, which makes me believe its substitution.
At first, I thought it was Insertion when they added the A, but i had to look back again and see that the 5 was removed.
Can't be duplication, since no number/letter was duplicated.
And it can't be Deletion, since another thing was inserted,
I hope this helps!!
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