@Gate Fever, but according to wording "either or" correct answer will be 30 as @Soumya29 did.
If it's either $2700$ $(or)$ $9000$ (but not both)$ →36+48−$(2∗27) $=30??$
How did you subtract $2\times27?$
@Lakshman Patel RJIT
it is symmetric diiff formula
$n(A\Delta B)=n(A)+n(B)-2n(A\cap B)$
@Lakshman Patel RJIT, Draw the Venn diagram you will get it :)
@Shubhgupta @Gate Fever I am also confused in this "either or" thing.
@Mk Utkarsh please check this once.
Case $(1):$Either $A$ $(or)$ $B$ but not both
Case $(2):$Either $A$ $(or)$ $B$ $(or)$ both