Question is above in the picture
2 answers:
Answer:
Known. The other answers are absurd.
Step-by-step explanation:
In geometry, often times you must have at least one angle to problem solve and find the rest. So having a known angle to build off of is important. Vertical Angles and Supplementary Angles are examples of things that require a known angle to find the rest. Why?
Say you only know one angle and the other is congruent to that angle, but across from it...Due to the theory of vertical angles, you now know the other side has to be the same/congruent. For supplementary angles, say you're dealing with a shape like the one I've attached. Once you have a or b, you can determine c. You have to know at least one of those angles to determine it's other unknown angles.
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Angle UTV is basically given: it's 138°.
Moreover, since UTV is isosceles, the other two angles have the same measure x. We thus have
So, TUV is 21°, and VUW is complementary, so it must be 69° so that they sum up to 90°