56
The way you figure this out is to first recall that Whole Numbers = 0, 1, 2, 3, 4, ...
Then, just start pairing numbers up:
0, 110
1, 109
2, 108
3, 107
and so forth.
What you realize is that you have a bunch of pairs of numbers that start with (0, 110) and end with (55, 55)
Once you get beyond 55, the pairs start repeating themselves:
(54, 56) is the same as (56, 54)
So, if you start with zero and go up to 55, you would have a total of 56 unique pairs of numbers that would sum to 110.
Hope this helps!
Good luck