Dennis will either purchase his mother' s house and live in San Diego, or else he will move to Miami, but Dennis will not do either of these unless he gets married  Dennis' s mother will let Dennis purchase her house only if she attends his wedding, but not otherwise
Ttherefore, Dennis will purchase his mother' s house and live in San Diego only if his mother attends his wedding
Dennis's mother would not let him move to Miami and buy her house too.