I am new to the site, can anyone help me on how to change the serpentine belt? Which bolt looses the pully? I have a 1999 rx300

there is a 12mm set bolt towards the front of the vehicle and facing the fender. then the 12mm bolt that loosens the alternator bracket is in the front of the alternator facing the radiator. if u have a little 1/4" drive rachet use that and a 12mm 1/4" drive socket. it takes a little while to slowly loosen the alternator so be patient. good luck