The correct option is C n=9
The total number of terms in binomial expansion are (n+1),
Therefore, 7th term from last will be (n−5)th term.
Given,
T7Tn−5=16
⇒nC6(2)13(n−6)(3)−13(6)nCn−6(2)13(6)(3)−13(n−6)=16
⇒n!6!(n−6)!(n−6)!6!n!(2)13(n−12)(3)−13(6−n+6)=16
⇒(6)13(n−12)=(6)−1
Equating the powers,
n−12=−3
So, n=9.