Astudent writes an incorrect step while checking if the sum of the measures of the two remote interior angles of triangle abc below is equal to the measure of the exterior angle.
step 1: m∠x + m∠y + m∠z = 90 degrees (sum of adjacent angles)
step 2: m∠w + m∠z = 180 degrees (supplementary angles)
step 3: therefore, m∠x + m∠y + m∠z = m∠w + m∠z
step 4: so, m∠x + m∠y = m∠w

in which step did the student first make a mistake and how can it be corrected?

step 1; it should be m∠x + m∠y + m∠z = 180 degrees (sum of angles of a triangle)
step 1; it should be m∠x + m∠y + m∠z = 180 degrees (corresponding angles)
step 2; it should be m∠w + m∠z = 90 degrees (supplementary angles)
step 2; it should be m∠w + m∠z = 90 degrees (adjacent angles)