Line r and t are parallel with unknown line intersecting them as a transversal. 138 degree is congruent to angle 2 because line r and t are parallel to each other. angle 2 and 5 are vertically opposite again so angle 5 is also 138 degrees. Now angle 5 and 6 are linear angles i. e summation of 5 and 6 is 180 degrees.
It is D. Angle 1 and 138 degrees are both equal, so angle one equals 138 degrees. This is because they are alternate interior angles, or exterior, not quite sure. Anyway, this means angle 1 and 2 are equal because of either alternate interior or exterior. Angle 4 and 2 are supplementary angles, meaning 138 + angle 4 = 180. This means angle 4 is 42 degrees. Because they are vertical angles, angles 4 and 6 are the same. So angle 6 is 42 degrees
