As it asks for the sine of the triangle, use SOHCAHTOA.
For sine, it is SOH, or:
SINE: opposite/hypotenuse.
We are looking at angle Y.
The opposite of angle Y is the side y
The hypotenuse (or the longest side, opposite over the right angle) is side z
Place the opposite over the hypotenuse
Opposite = y
Hypotenuse = z
y/z, or option J, is your answer
Hope this helps