Question 84982
In a 90-60-30 triangle the shortest side will be the side opposite the smallest angle.
The side opposite 30 angle will be the shortest one.

We can use the sine ratio.
     now, sin 30 =  opp side / hypotaneus
           1/2 =   opp side / 18
       hence opp side =  9
That is the length of the shortest side.