Question 494807
Since the length of the pole is unchanged, using the Pythagorean Theorem we write:

{{{x^2+15^2=(x-13)^2+(15+9)^2}}}, where x is the initial height of the wall.

Solving this equation we get:{{{x^2+225=x^2-26x+169+576}}} => x=20.

Since the initial height of the wall was 20 m, using Pythagorean theorem we get the length of the pole:

{{{sqrt(20^2+15^2)=sqrt(400+225)=sqrt(625)=25 m}}}