You are given a sequence: 100, X1, X2, 115. We have to find the missing value Xi. It is given that Xi will be average of prev and next value & will be an integer. Here X1 will be 105 and X2 will be 110.

There could be more values missing.

If you think this question is from an ongoing contest please post the link of the contest and I will delete this post. ( I got it from my classmate ).