Answer:
9 cm
Explanation:
Given that angle Y = 90 means that the triangle is a right angle triangle
If angle X = 30 degrees and xz =18 cm
xz is the hypotenuse side while zy is the opposite side considering the angle at X
Hence using the notation SOH CAH TOA
SOH
Sin X = zy/xz
Substituting
Sin 30 = zy/18
cross multiply
zy = 18 sin 30
zy = 18 * 0.5
= 9 cm