From the given figure, it can be seen that 13x = 15x - 8 because they are vertical angles and thus are equal.
13x = 15x - 8
15x - 13x = 8
2x = 8
x = 8/2 = 4
Thus, 15x - 8 = 15(4) - 8 = 60 - 8 = 52.
RT is a diameter, which means that mRT = 180
mRV + mVU + 52 = 180
mRV + mVU = 180 - 52 = 128
Now, given that mRV = mVU,
Thus, 2mVU = 128
Therefore, mVU = 128 / 2 = 64°