Answer:  B. 1/2(y - 116) = 64    
Step-by-step explanation:
Since, we know that, 
The angle formed by two tangent = [tex]\frac{1}{2}(\text{Difference of intercepted Arcs} )[/tex]  
= [tex]\frac{\text{major arc - minor arc}}{2}[/tex]
Here, Major arc = y° 
Minor arc = 116°
And, Angle made by two tangents YX and YZ,
 [tex]m\angle XYZ = \frac{\text{y - 116}}{2}[/tex]
[tex]64 = \frac{\text{y - 116}}{2}[/tex]  ( because,  [tex]m\angle XYZ = 64^{\circ}[/tex] )
⇒ [tex]\frac{\text{y - 116}}{2} = 64[/tex]
Which is the required equation to find y,  the measure of XWZ.
Thus, Option B is correct.