you so so much in advance!

dont answer if you dont know ! i don't want to have to report just because you wanna take my points ///:

1. ab is shortest, ac is middle, and bc is the longest. 
2. one, yes. second one, no
3. IDK

1.) the longest side is BC
the second to longest side is BA
and the shortest side is AC 
(don't let the drawing fool you, look at the angles)

2.) a. 5, 9, 12

3.) The third side can be approx. 7.8 m

Hope this helps ;)