Big Book (Old GRE) Test #2 Section 5 Ex 15

Any help with this one would be greatly appreciated!
2

Use the vertical opposite angle property and sum of exterior angle of the triangle property and you’ll find the answer

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Answer is C btw. Both quantities are same.

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Thank you everyone!
I will put the baby steps below, for anyone in the future that has issues with this problem as well.

  1. Vertically opposite angles (vert. opp. ∠ s) are the angles opposite each other when two lines intersect. Vertically opposite angles are always equal . So the angle opposite to x degrees is also x degrees. And the other two opposite angles in that circular area would be 180-x degrees.
    This is holds true for all corners on this triangle.

  2. The sum of interior angles of a triangle is 180 degrees.
    So, y+x+(180-Z)=180
    y+x-z=0
    Thus, y=z-x.

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