Gary is cleaning windows. He sets his ladder 25 feet away from the wall of the house to reach the windows on the second story, which are at a height of 20 feet above the ground. He moves his ladder 15 feet closer to the wall to reach the windows on the third story of the house.
third-story
window
second-story
window
ladder
20 feet
15 feet
25 feet
Approximately how high above the ground are the windows on the third story of the house?