Step-by-step explanation:
Statement . . . . Reason
1. ∠1 ≅ ∠2, ∠J ≅ ∠K . . . . given
2. AB ≅ BA . . . . reflexive property of congruence
3. ΔABK ≅ ΔBAJ . . . . AAS congruence postulate
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The shared side is congruent with itself. Two angles are said to be congruent, and one of those is adjacent to the shared side. This is the setup for claiming AAS congruence.
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Additional comment
It is a good idea to be familiar with the ways triangle congruence can be claimed. There are basically 4 of them: SSS, SAS, ASA, AAS. The special case of two sides and an angle can only be claimed in the form of HL for right triangles.
In these abbreviations, S represents a side; A represents an angle. The order is important: SAS represents the case of the angle being between the two sides, for example.