Can Anyone explain how to find max of (a(1)+a(2n), a(2) + a(2n-1)..a(n)+a(n+1)) if array elements are {3 4 6 7 8 9} in a simpler way?

I am a beginner and learning coding. I am only able to find the maximum or sum of the elements in the array. I could use some help in understanding how this arrays are paired. I wanted to know how this array is paired in such way to get that max as result.