Answer
A) Y+Z=90
B) AB is perpendicular to BC
Work Step by Step
A) For the two lines to be parallel, we know that the two edge angles must be right angles. Thus, it follows that Y+Z must be equal to 90 degrees.
B) We know that if the two lines are parallel, then the lines connecting those the opposite ends of the two lines must be perpendicular. Thus, AB and BC must be perpendicular.
