Q:

Can i mark multiple answers as correct?

For example if 2 users answered my questioned, and both of them helped me, and both give useful but different answers, what should I do?

A:

No. You can vote for both but there can only be one...

... accepted answer. If you're really stuck, and both do the same thing (or roughly), and you can't pick a technical benefit of one over the other, or even the quality of the writing, give it to the post (hover over the time eg "45 mins ago" for a precise version).
But it's really up to you.

