How to solve the problem !!!

You have to separate the 4 triangles and then :
1. Find out the angle
2. With the angle find the missing value

A.


Now that you now how , do the same with the other 3 :


B.



C.


D.



And now after you finish the only thing you have to do is to add all the sides of field , that will give you the amount of rope he needs to buy .