How do I know if shop is telling me truth about needind rears brake pads,rotors

Thanks... Do you think car with 75k would need new rotors...they are saying that they do not machine these at all because they are thin !!! to start with...and they are saying pads have about 2 percent left

75,000 is a reasonable amount of time for replacement. Would not be surprised if they are telling you the truth. Most places do not machine rotors anymore.