How do I convince my parents to let me stay in boxing? i need boxers advice?

they think it's a waste of time I box from mon-thru from 9-10:30 and I run in the morning. they have to pay 79.99 a month which I have to admit it is a lot. but I have a good feeling that I can go far in this sport. what can I do to convince them they are threatening to cancel the membership if I don't soon. I really absolutely enjoy this sport. there isn't a any gyms close by that's the only gym that is registered in USA boxing. I tried looking for a job but no one called back