how can I compare to texts and extract only the difference text into the other cell

I need to compare to cells and then extract only the difference to the third cell. I want to have the result like in column C and would be great if I do not need to use VBA, I use microsoft 365. Please kindly help.

I tried with substitute but it did not work because it return the whole text that difference. =Substitute(A2;B2;"") the result Iam17yearsold. But I only want 7 for the answer.

Assuming TAB, char(8), is not part of your texts to compare, using that as a delimiter:

• compare characters in b with a
  • using 'If start_num is greater than the length of text, MID/MIDB returns "" (empty text'
• replace with the delimiter if equal
• split by delimiter, ignoring blanks and join

=LET(
    extract_diff, LAMBDA(a, b,
        LET(
            idx, SEQUENCE(, MAX(LEN(a), LEN(b))),
            b, MID(b, idx, 1),
            delim, CHAR(8),
            ARRAYTOTEXT(
                TEXTSPLIT(CONCAT(IF(MID(a, idx, 1) <> b, b, delim)), delim, , TRUE)
            )
        )
    ),
    MAP(A2:A3, B2:B3, extract_diff)
)