How can i convince my parents to get me this car while i'm...?

In Australia. All i know is that it's a White Chevy Impala and it's for sale along State Route 33 for 9800. I drive this piece 1998 Isuzu trooper that gets 15 miles to the gallon and i hate feeling it up at least twice a week during the school year or if i go anywhere after school than that's three times, and i hate. I mean i'd like to get out of the house but how can i, when i'm worried about getting gas all the time.