Answer:
Value of k = 10
Explanation:
Exterior angle property states that the exterior angle is equal to the sum of the opposite sides of an interior angle.
As per the diagram:
In triangle XZY:
,
and

By definition of exterior angle property we have;

Substitute the values and solve for k.

Combine like terms;

Subtract 15 from both sides we have;

Divide both sides by 10 we have;
k = 10
Therefore, the value of k is, 10