2007 Ford Focus serpnitine belt

Jack up front end, remove passenger side front wheel and plastic splash guard. Tensioner has (I think) a 15-mm bolt at the pulley end. Force the tensioner to give slack on the serp belt. You'll need some dexterity to work around the close confines space, but with a little patience and and assistant, you can remove the belt. Be sure to check both the idler pulley and tensioner pulley for abnormal noise. These pulleys are common to go bad / need replacement.

Take special note of how the belt runs before you pull it off. It twists and winds around quite interesting. If you forget, you'll be scratching your head trying to remember how it goes on again.