+1084 I dont think I should do your homework for you, but I can give you a hint.
For 1)
Rotationally use the Law of Cosines until you got one of each.
Ex: First set angle B to C, then angle A, and so on.
For 2)
Use the law of cosines (again) to get a quadratic. The larger term is a_2, and the smaller term is a_1. (Further hint, the cosine of 60 is \(\frac{\sqrt3}{2}\))
For 3)
Use the law of cosines, where 12 is c, 10 is b, and a is a.
