Find the sum of the first fifteen terms of an arithmetic sequence if the middle term is 92.

I'll try to explain this as much as possible but 92 is x but you don't know y 
so it would be dermined this way I hope this makes sense 
15-8=7 So, this would mean that the term is 7th in place. 
92-7y+92+7y=92+92=184 

What is the question ehre

The answer is -pie over 2