We will use the leg rule
hypotenuse leg
----------------- = --------------------
leg part
y 9+11
------- = -----
11 y
Using cross products
y^2 = 11(20)
y^2 =220
Taking the square root
y = 2 sqrt(55)
Now we can find z using the Pythagorean theorem
11^2 + z^2 = y^2
121 + z^2 = 220
z^2 =99
z = 3 sqrt(11)