Use the Law of Sines (sina/A=sinb/B=sinc/C for any triangle)
YZ/sin30=50/sin90
YZ=50sin30 (sin90=1 :P)
YZ=25m
Use the 30,60,90° triangle ratios 1, √3, 2
YZ/1=50/2
YZ=25m
Using the Pythagorean Theorem....
(2*25)^2=YZ^2+(√3*YZ)^2
2500=YZ^2+3YZ^2
2500=4YZ^2
625=YZ^2
25m=YZ