Answer:
Vertical Angles!
Explanation:
Very simple!
Vertical angles are a pair of angles that are equal in degree measure.
Essentially, they are equal to each other. Nothing more to it.
This means that
!
I presume you have done math before, so this solves to be:
(I don't have a degree sign, but it should be there in your answer.)
Hope this helps!
P.S. How's life?