Once upon a time a brave and mathematically-inclined warrior named Al Jebra set out on a quest to rescue the kidnapped Princess Polly Nomial. First, Al needed to get to the room of the stolen Princess to read the ransom note left behind. The Princess lived in the tower with no stairs (for security purposes, ironically). Al plans to use his 17 ft ladder to climb in a window 15 ft up the tower wall.

How far from the wall should Al position the bottom of the ladder so that the top reaches the window ledge? The ladder is 17 ft long.