How much did briana save by purchasing a backpack that cost $45 with a sales promotion of 20% off instead of a backpack that cost $42 with a sales promotion of 10% off? $

you don't if you paid you paid. it's like if i bought a computer and used it then i say idon't want it anymore so im gonna return it. you can't. unlkess you have your reciept

answer; the correct answer should be (demonstrations); good luck