My 2014 F150 only has 27,000 miles and the rear brakes are scraping. Is this Normal? I always thought the fronts go first .?

The rears usually last a long time. I doubt the brake pads are worn out unless you always have one foot on the brake. More than likely the brake calipers just need to be serviced by lubricating them and replacing the hardware parts. Take off a rear wheel to check if you actually need new brake pads or if you just need the calibers serviced before taking it to a shop.

https://www.youtube.com/watch?v=1XFgRXBaDmU

Msy have a stone caught somewhere

Do you have drum brakes in the rear? If you do brake dust can build up inside the drums and cause brake noise. If you have compressed air blow the drums out from the area by the backing plates.

If you can't do this yourself go to a mechanic for a rear brake service.

I've had customers think the noise was coming from the rear and it was actually the front brakes grinding. Try braking next to a building so you can hear better.

could be a stone caught in the dust plate ( disks)or an over adjusted parking brake, try reversing hard then braking hard ( on an empty road)