Since this involves right triangle, use Pythagorean Theorem.
the length of the rope serves as the hypotenuse while
the length of the pole is the length of one leg
Let 'x' be the distance of the base of the pole to the end of the rope
[tex]x^2 = 15^2 - 7^2[/tex]
[tex]x^2 = 176[/tex]
[tex]x = 4 \sqrt{11} [/tex]
or
[tex]x = 13.266meters[/tex]
----------------------------------
See attachment below for the illustration