This is from my book on discrete and combinatorial mathematics, in the chapter about combinations (just for clarity, this stuff Combination - Wikipedia, the free encyclopedia , but you probably new that). Considering the chapter it is from, simply filling it in shouldn't be the way they expect you to solve it. I probably have to use some sort of binominal coefficients. No idea how to apply it in this case, though...
It shouldn't be too hard, considering it is from the beginning of the book (and from a first year's course), but I simply have no idea.
All the exercise says is this: "Determine the value of each the following summations"
Do you really think I should merely enter the numbers and add them up? It just seems too easy, especially since the chapter they're from isn't about summations at all. It is about combinations.