Help understanding these concepts

Hello everyone! Thank you all for your time. I'm trying to freshen up for the upcoming school year with math stuff (my worst subject), and theres several concepts I just can't get down. If someone could explain how you arrived at the answer that would be tremendous, thanks!

(1)The first concept is seen with the equation 14!/1!13!. I just don't understand what I'm supposed to be doing with it.

(2) The next one seemed at first easy to me, but I keep getting it wrong. It simply shows 5x=2. Now I thought I'd simply divide both sides by 5, and get x=2/5, but the answers all have the letter "e" in it. I have no idea why though :(

and lastly, (3) I don't know how to find all the possible number of imaginary zeros of *f*(*x*) = 2*x*3 - 4*x*2 + 8*x* - 3 I think I just don't do well with the more odd numbers (i, !, and so on). Thank you very much, I hope this isn't to much of a bother. Thanks!

-Cillian3