This can have two scenarios: Angle J is the vertex and angle K is one of the base angles, or angle K is the vertex and angle J is one of the base angles. We can check this easily by seeing if they add up to 180.
Checking if the base angle is 72, we see that it fits, because 36+2(72)=180. Thus, the two base angles are angles J and L. Angle L is 72°.
