Answer:
15 meters
Explanation:
Because angle BFD and angle DFC are supplementary (they form a 180 degree angle, as you can see from the fact that they both form a straight line) and angle BFD is 90 degrees, angle DFC must also be 90 degrees. Since it is 90 degrees, you can use the Pythagorean theorem to solve for DF as a part of triangle DFC=> 8^2(x^2)=17^2.
=>64(x^2)=289
subtract 64 from both sides=> x^2=225
take the square root of both sides=> x=15
Since triangles BED and BFD are equal by way of angle-side-angle, we know that all of their corresponding sides and angles are equal, and therefore, DF=DE, so DE=15 meters