Answer:
514 feet
Explanation:
Just simply use the pythagorean thereom:
a^2 +b^2 = c^2 (or if you are a nerd (a+bi)(a-bi) = c^2)
plug in the values of a, b, and c with the side lengths of the triangle:
x feet, 64 feet, and x+4 feet
x^2 +64^2 = (x+4)^2 , thus x =510
the hypotenuse = x+4 feet = 510 + 4 = 514
ANSWER: 514 feet