"From how many people are those letters?"
Translation:Od kolika lidí jsou ty dopisy?
Ok, this is the second time we've seen kolika in this lesson. I did a little more digging since I was able to answer at least part of my own question in the previous comment. Kolika is obviously a form of kolik that is used in genitive expressions.
Well, a little more digging revealed that kolik, though an adverb, declines. I had to go to the Czech wiktionary, which though I can't yet read, I can look at declension tables.