Question

In triangle XYZ, m∠Y is 3 times larger than the m∠X. The exterior angle at Z measures 120°. What is the m∠X?

Answer 1

• An exterior ∠ is equal to the addition of the two Δ angles not right next to it.

140º = 60º + 80º;        120º = 80º + 40º;

100º = 60º + 40º  

• An exterior angle is supplementary to its adjacent Δ angle. 140º is supp to 40º

• The 2 exterior angles at each vertex are = in measure because they are vertical angles.

• The exterior angles (taken one at a vertex) always total 360º