What should come at the place of the question mark (?) in the following series?
2, 3, 8, 9, 26, 27, ?

The correct answer is 80.

Let us analyze the logical pattern in the given numerical series:
2, 3, 8, 9, 26, 27, ?

We can observe that the series consists of pairs of numbers or follows a simple pattern based on powers of 3:

First term:
$3^1-1=3-1=2$

Second term:
$3^1=3$

Third term:
$3^2-1=9-1=8$

Fourth term:
$3^2=9$

Fifth term:
$3^3-1=27-1=26$

Sixth term:
$3^3=27$

Following this alternating rule ($3^{\mathrm{n}}-1$ followed by $3^{\mathrm{n}}$), the seventh term for $\mathrm{n}=4$ must be:
$3^4-1=81-1=80$

Alternatively, looking at the odd-positioned terms:
1st term: 2
3rd term: 8 = (2 × 3) + 2
5th term: 26 = (8 × 3) + 2
7th term: ? = (26 × 3) + 2 = 78 + 2 = 80

Therefore, the number that replaces the question mark (?) is 80.