The best response to prove that the two triangles are congruent is:
He could apply the concept of HL and show that the two triangles are congruent.
The Hypotenuse-Leg (HL) theorem states that if you have two right triangles, and you know the lengths of the hypotenuse and one leg in each triangle, the triangles are congruent if those lengths are the same. In this case, both triangles have a hypotenuse of 13 units, and for the first triangle, one leg is 12 units, and for the second triangle, one leg is 5 units. To complete the proof, the third side should also be calculated using the Pythagorean theorem, but based on the provided information with HL, we can conclude that they could potentially be congruent if both legs match.