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Review: Interior and Exterior Angles of Triangle
Explanation
In this question, the fact that the two vertical lines are
both perpendicular to a common line means they are parallel to each other. That
means that the angle just "under" y
is equal to x, and since it is
supplementary to that angle, and that angle is 40, 
.
Moreover, since z is the third angle
in a triangle with angles of 90 and 40 degrees, 
.
Therefore, 
.
The correct answer is (D).
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