See attached picture and check solution below. We are given with the following values: A = length of transmission line = 96ft B = length of shadow = 72 feet C = distance of ladder to base of transmission line = 66 feet
Solve for angle created between the wire and tip of the shadow: tan x = opposite/ adjacent tan x = 96 feet / 72 feet x = 53.13°
Solving for the height of the ladder: tan x = Ladder length / (72-66) tan 53.13° * (72-66) = ladder length ladder length = 8 feet