Let the distance between the tops of the poles is the distance between points A and B.
We can see from the given figure that points A, B and C form a right triangle, with AB as the hypotenuse.
By using the Pythagoras Theorem in △ABC, we get
(11−6)2 + 122 = AB2
AB2 = 25 + 144
AB2 = 169
AB = 13
Hence, the distance between the tops of the poles is 13 m.