Answer
$1430$
Work Step by Step
Sum of the an arithmetic series can be calculated by using formula $S_n=\dfrac{n}{2}(2a_1+(n-1)d)$
Our aim is to determine a formula for the general term of the arithmetic sequence $a_n$.
Such as: $a_n=a_1+(n-1)d$
For $n=26$
$s_{26}=13(a_1+a_{26})$ ...(1)
Now, $a_n=a_1+(n-1)d$
$\implies a_{26}=a_1+(25)(2)=80$
From equation (1), we have
$s_{26}=13(30+80)=1430$
