Algorithm to find the closest summation of elements in a list to a given number

Say I have a list {1,3,7,2,11,8,2} and I want to take x elements from the list and get the value 15.5.

Is there an algorithm that would give me x elements in a list that, when added together, get nearest to this given value?

There is no preferred amount of elements, I just want to get as close to the given as possible.

I plan on implementing this algorithm in Swift (Object Oriented) if that makes any difference.