Question about Sysmin with pole zero canellation

hi everyone i know that minreal commmand reduces the system by cancelling pole zero ,,,but my question is if i have 6 states ,,whose controllability is 5 (means there must be one pole zero cancellation) but which state or pole has been cancelled? 1.how to find it? next suppose the state of my interest is x5 which is (position of my system) and if 2.that has been cancelled then what should we do? next the reduced system can be used further to augment with other subsystem? please help me < if any one consider himself be the guru of Control system > by further asking question please answer me these questions thanks in advance