Transitive property states that, if two segments (or angles) are congruent to congruent segments (or angles), then they’re congruent to each other. Since triangle ABC is congruent to triangle DEF and that implies, the angles of triangle ABC is congruent to angles of triangle DEF and since it is given that triangle DEF is congruent to triangle GHI, that implies the angles of triangle DEF is congruent to angles of triangle GHI. Therefore, the angles of triangle ABC is congruent to angles of triangle GHI. So, The triangle ABC is congruent to triangle GHI by the transitive property.