What are the adjectives in this sentence upon reflection Riley decided that the best course of action would be to step down as president of the board

What is the missing statement in step 3 of the proof? given: z1 is complementary to 22. 22 is complementary to 23. prove: m_1 = m23 m21 = m2 m2 1 + m22 = 90° m22 = m23 m22 + m23 = 180° 2 statements 21 is comp. to 22 2. 22 is comp. to 23 3. ? 4. mz1 - 90°-m22 m22+m23 = 90° 6. m23 = 90°-m22 7 m21 - m23 reasons 1. given 2. given 3. def of comp. zs 4. subtr equality prop. 5. def. of comp. 25 6 subtr. equality prop 17. trans. prop. vo