Which theorem or postulate states that if the hypotenuse and an acute angle of one right triangle are congruent to the hypotenuse and corresponding acute angle of another right triangle, then the triangles are congruent?
In right-triangles, if one of the acute angles are congruent, the other is also, since the acute angles are complementary.
Therefore we are in a situation where all three angles are congruent.
If we add one congruent side (hypotenuse), congruence of the two triangles is assured by the ASA (angle-side-angle) postulate.