Explani the RSA cryptosystem by showing coding and decoding of the word Birthday if the public key is known to be $(101, 3)$. Consider each alphabet as 1-digit base 100-number.
I know how to code it. Only I want to ask what is the meaning of $\textbf{ Consider each alphabet as 1-digit base 100-number}$.
It's not a standard terminology. I suspect the author actually missed some words and meant "consider each letter of the alphabet ..." though that's still far from a standard way to phrase things.
My best guess is that they're encoding each letter as a number between 0 and 100, probably with the scheme
and then encrypting each letter separately.
(This is a rather bad way of using RSA -- in addition to the brute-forcing opportunity inherent in only having 26 different messages, there's the fact that the number 1 always encrypts to itself. Check if your source material defines a concrete coding somewhere else).