Answer:
a. When you have two parallel lines cut by a transversal, angles 4 and 6 become same side interior angles, meaning they add to 180 degrees. Alex's mistake is that he thought angles 4 and 6 were corresponding angles, which are equal to each other (corresponding angles would be like angles 2 and 6. they are in the same place in relation to the transversal and the parallel lines. if you moved line l down, angle 2 would be on the same spot as angle 6, so they are corresponding angles).
b. angles 4 = 140 degrees
Explanation:
a. Alex thought that angles 6 and 4 were corresponding angles, however, they are same side interior angles. Because two parallel lines are cut by a transversal, we can conclude that angles 4 and 6 are same side interior angles.
Same side interior angles are angles that add to 180, so you would do 180-40 to get angle 4. the measure of angle 4 would be 140 degrees (the answer to b).