The value of y is y = 107 since angle y and the 107 degree angle are vertical angles. Vertical angles are always congruent. You could also do x+y = 180, plug in x = 73, and solve for y to get y = 107.
Since the other pair of vertical angles is x and z, this means x = z = 73. Or you could solve z+107 = 180 to get z = 73.
