2077
Explanation
To find the sum of an arithmetic sequence, use the formula
[tex]\begin{gathered} S_n=n(\frac{a_1+a_n}{2}) \\ \text{where} \\ n=the\text{ number of terms being added} \\ a_1=the\text{ firs term} \\ a_n=the\text{ nth term}(\text{ last term)} \end{gathered}[/tex]Step 1
Let
[tex]\begin{gathered} a_1=7 \\ n=31 \\ a_n=127 \end{gathered}[/tex]now, replace and calculate
[tex]\begin{gathered} S_n=n(\frac{a_1+a_n}{2}) \\ S_n=31(\frac{7+127}{2}) \\ S_n=31(\frac{134}{2}) \\ S_n=31(67) \\ S_n=2077 \end{gathered}[/tex]therefore, the answer is
2077
I hope this helps you