How to convince my mom to let me get a dog?

ok so my goldfish just died and i really want a dog and I've wanted one for awhile. i want a poodle. i have done everything she has asked but she doesnt want to get me one. she had a dog when she was little it was a beagle named bobbi.she loved it.every time i ask her she gets really POed so can u tell me how to convince her by the way im 11 and my brother is 13 so help