Step 1: m∠m + m∠n + m∠o = 180 degrees (sum of angles of a triangle)
Step 2: m∠p − m∠o = 90 degrees (alternate interior angles) : <em>It's incorrect step because m<p and m<0 are on a common point on a line and make a linear pair. Therefore, m<p and m<0 are supplementary angles.</em>
Step 3: Therefore, m∠m + m∠n + m∠o = m∠o + m∠p.
Step 4: So, m∠m + m∠n = m∠p.
<h3>Therefore, student did mistake in 2nd step and correct step should be Step 2; it should be m∠o + m∠p = 180 degrees (supplementary angles).</h3>