He could apply the concept of HL and show that the two triangles are congruent.
In this case, HL (Hypotenuse-Leg) is a valid method for proving the congruence of right triangles. Both triangles have a hypotenuse of 13 units, and if we can find that one leg of the first triangle (12 units) and one leg of the second triangle (5 units) can be related to a third leg by the Pythagorean theorem, we could show their congruence using HL. However, it's important to note that based on the specific dimensions provided, these triangles would not actually be congruent, as the side lengths are different. So the response indicating they could be proven congruent using HL would be correct only in hypothetical situations where the dimensions satisfy the congruence criteria.