Answer:
3
Step-by-step explanation:
You know that angle Y is a right angle because XY is the radius and YZ is a tangent to the circle. So, you can use the pythagorean theorem to find the third side:
XY^2+4^2=5^2
XY^2+16=25
XY^2=9
XY=3
Hope this was helpful! :)
