Answer:
15 feet
Explanation:
Pythagorean theorem:
a^2 + b^2 = c^2
a = height of the pole = 9 feet
b = distance from the pole to the tower = 12 feet
c = length of the guy wire (hypotenuse)
the equation:
9^2 + 12^2 = c^2
81 + 144 = c^2
225 = c^2
c = √225
c = 15 feet