Question

Can anyone explain this to me?

Answer 1

Yes, because of the Angle Angle Similarity Property.  Angle U in the larger triangle measures 55 degrees.  Angle X of the smaller triangle is unknown, but in the polygon formed by the smaller triangle inside the larger, X is equal to 125. Since both values of X form a straight line, they must add up to 180.  So subtract 125 from 180 and you get 55.  This would prove that at least one angle is equal, and then if you look at the top angles of the triangle, they both have Angle U, so they must also be equal.  The third choice is correct.