Answer:
11 - not enough information
12 - yes, Angle-Angle-Side (AAS)
13 - yes, Side-Angle-Side (SAS)
14 - yes, Angle-Side-Angle (ASA)
15 - yes, ASA
16 - yes, Side-Side-Side (SSS)
17 - yes, ASA
18 - yes, SSS
19 - no (different from "not enough information")
20 - yes, AAS
Explanation:
11 - 1 pair of congruent sides is given; can conclude 1 pair of angles is ≅ by vertical angles; need 3 parts to prove congruence
12 - 1 pair of sides and a pair of angles given ≅; can show vertical angles ≅
13 - the side that's shared by the two triangles is the second ≅ side
14 - in addition to what's given, can show vertical angles ≅
15 - in addition to what's given, can show vertical angles ≅
16 - all given
17 - in addition to what's given, can show shared side ≅
18 - ..., shared side
19 - the congruent parts are not in the same order on each triangle
20 - all given