Answer
$3775$
Work Step by Step
Formula to calculate the sum of an arithmetic sequence is: $S_n=\dfrac{n}{2}(a_1+a_n)$ ...(1)
Here, $a_1: $ First term and $d=$ common difference
Since, we have $d=a_2-a_1=19-7=12$
and $a_{25}=7+12(25-1)=295$
Then, our first (1) equation becomes: $S_{25}=\dfrac{25}{2}(7+295)=\dfrac{25}{2}(302)=3775$