I don't get this maths question - bearings - please help!?

I am not looking for the answer, but for an explanation on how to do it - this was on my specimen paper and I do not get how to do it!



It says...



A ship leaves port %26amp; sails on a bearing of 130 for 3km. The ship then changes course and sails on a bearing of 240 for 7 km. Calculate the distance of the ship from the port (marked a on the diagram).



Then there's a diagram (please excuse my drawing):

http://i44.tinypic.com/11tswnq.jpgI don't get this maths question - bearings - please help!?
You have accurately described the ship's path in your diagram so you know the two sides of a triangle (3km %26amp; 7km) and the included angle (70 degrees). I'm not sure what level you are at but given this information and some basic trigonometry you should be able to calculate the third side of the triangle, i.e. the distance from the port (6.6 km?)I don't get this maths question - bearings - please help!?
tbh i was about to ask the same question cos i dont have the slightest clue on how this works.

soz i cant help.