Answer:
Step 3; it should be m∠m + m∠n + m∠o = m∠o + m∠p
Step-by-step explanation:
We are given that,
Triangle ABC having three interior angles ∠m, ∠n and ∠o and an exterior angle ∠p.
It is required to prove m∠m + m∠n = m∠p
Now, according to the steps shown by the student, we see that,
From step 1, we have, m∠m + m∠n + m∠o = 180°
From step 2, we have, m∠p + m∠o = 180°
Thus, in step 3, we get, m∠m + m∠n + m∠o = m∠p + m∠o.
But, the student did m∠m + m∠n + m∠o = m∠p + m∠n, which is wrong.
Thus, the student made the mistake in step 3 as the relation should be m∠m + m∠n + m∠o = m∠p + m∠o.