I think it is none of the above
Theorem 20 says that if 2 sides of a triangle are congruent then the opposite sides are congruent, but they only give you one side.
Theorem 21 says that if 2 angles of a triangle are congruent than the sides that are opposite of the angles are congruent, but they are two different triangles
Theorem 22 says that if 2 sides of the triangle are not congruent then the angles opposite them are not congruent and the larger angle is the angle opposite the longest side
