There's no even remotely healthy way to lose that much in one week.
Even 20 pounds a month would be an unhealthy loss rare.
W/o personal support of a dietician and a doctor, a loss rate of 1-3 lbs/week is about the best you can expect.
The weight didn't go on that fast, so it's not going to come off that fast.
54% of your total weight is a lot to lose. You must consult a doctor. If you succeed, you will weigh 170 pounds after it's all over.
170 lbs...
170 / 14 = 12.1428571 stone
170 pounds
170 pounds = 77110.7029 grams
If you 14 and weigh 170 pounds, then you are too old and fat to dance ballet. Overweight does not mean you cannot dance.
Is it safe
170 pounds and 6ft 3in
probly 160-170 pounds
around 170 pounds
145--5'11"
Apart from getting radical surgery, or getting really, really ill - you can't. A reasonable loss rate is something like 2-4 lbs/week, so don't even try.