How should I prove this???

Since UVX is 90 degrees Angle 6 and Angle 5 are complementary. Then, Angle 5 and Angle 4 are the same since they were bisected by WVY. This makes Angle 4 and Angle 5 the same, so you can say that Angle 6 + Angle 5 are complementary and Angle 6 and Angle 4 are complementary.

Where is the qeustion