Arithmetic Progression question on finding the 25th term In AP, sum of n terms is $\dfrac{3n^2 + 5n}{2}$. Find 25th term.
My work :
$S_n = \dfrac{n}{2}\left({3n + 5}\right)$
$2a + (n-1)d = \left({3n + 5}\right)$
$2a + 24d = 80$
$a + 12d = 40$
13th term is 40.
Bit we need 25th term! Please help

Hint: The $n^{th}$ term is the difference of sum of the first $n$ terms and sum of first $(n-1)$ terms. Mathematically, $$T_n=S_n-S_{n-1}$$
