First, we use the pythagorean theorem in the lower right triangle (with sides 4,x,6) and find x^2+4^2=6^2 and therefore x^2=6^2-4^2=20 so x=√20 which is approximately 4.5.
Also, we can see from the picture that z=y+4, and therefore the only option left is x=4.5,y=5,z=9.
