Answer:
Replace m<3 = 90 . Derived from applying statement (2) in statement (4)
Explanation:
The exercise is a one by one step proof of complementary angles. As in statement 2 we have proven that m<3 is 90 degrees and in statement 4 that m<1+m<2+m<3 is 180 degrees, we only need to replace statement 2 conclusion into statement 4 conclusion , as there in no reason for any further proof.
In the next reasons we must prove that the other angles measure 90 degrees which will allow us to conclude that both angles are complementary ( sum 90 degrees).