More likley then not , that the shoes are rusted on to the drum of the back brake disc .Wheel off and tap the drum with a malet .Or you might need to do it with hammer .Pump in the adjuster hole a penetrating fluid as the shoes will be toast by now. And if the disc is bad, you wont have to bother on how hard you tap it . Thats if the cable is free on the rear , if not , you need to remove the tension off the cable , so you can pull off the brake disc drum.