Question 884779
If n = how many consecutive terms starting at n=1, then the summation for the consecutive integers is  {{{(n/2)(First+Last)}}}.


Your first summation is 79 terms, and your second summation is 61 terms.


Notice, your question is "what is the average of x and y"?  As asked, that means to find  {{{(x+y)/2}}}.


{{{x=(79/2)(1+79)}}}; and  {{{y=(61/2)(80+15)}}}.


Fill-in the parts step by step and compute the answer.
Undone here, so you do that.