How to Convince My Mom to Let Me Adopt a Dog? :)?

I'm 13, and I REALLY want my own pet! We already have 4 household dogs that we adopted, but I don't think that they really like me. When I asked my mom if I could adopt a dog, she said that I get bored of the household dogs after 2 days. But, like I said I don't think they really like me. The reason for that is because my mom or my younger brother and sister get to them before me. If I had my own dog, I would HAVE to feed them, take care of them, and play with them. The dog would stay in my room, and I would do chores to pay for the dog and it's food, crate, toys, shots, medications, etc. I really do think I'm responsible enough for one, I have babysat other peoples kids for Pete's sake! I've even got paid more for doing extra! When we got out of school I had an A average for all subjects in the whole year. So, how can I convince my mom to let me adopt a dog? If I can get a dog, I will FOR SURE adopt a dog. Some of them have never even experience real human love, and they can get put down. Thank you!