Trig help

[aleezasss]

1. 
   A bridge spans a river, and the two identical sections of the bridge, each of length x metres, can be raised to allow tall boats to pass. When the two sections are fully raised, they are each inclined at 50° to the horizontal, and there is an 18-metre gap between them, as shown in the diagram. Calculate the width of the river in metres, correct to one decimal place.
   

 

[tkhunny]

Draw two perpendiculars to the low bridge position, through the ends of the bridge sections in the raised position.