15 cm
7.5cm
10 cm
5 cm

Answer:
7.5 = OM
Step-by-step explanation:
Since this is a right triangle, we can use trig functions
sin theta = opposite side / hypotenuse
sin 30 = OM / UN
sin 30 = OM / 15
15 sin 30 = OM
7.5 = OM