If you extend the line from m to n, it forms a triangle.

The first angle of the triangle is

z.

Since, sum of angles in a straight line is 180 degree, the second angle of the triangle is

180-yThe angle on the line n would be 180 - x because the alternate interior angles are supplementary.

Since, sum of angles in a straight line is 180 degree, the third angle of the triangle is

xThe angles of the triangle is z,x and 180-y.

Since the sum of the angles in a triangle is 180 degree,

z + x + 180 - y = 180

z + x = y(Option D)

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