weight loss plan to lose 6 lbs?

hi im 15 i would like to lose 6 lbs in about 3 weeks. i was thinking that i would take in about 800 calories a day and do a cardio workout for about 30 minutes every day. would this be effective?

will this weight loss plan work?

I am starting a new weight loss "diet" that I have created and I want to get some feed back on it before I start. Iam currently 5'1 and weigh around 130, so I would like to lose about 20 lbs.

What should I do about my weight loss plan?

I'm 18 years old and 5 feet 7/8 inches tall. I was taking phentermine the diet pill to lose weight before I started taking it I weighed about 160 lbs and now I weigh 153 lbs. I stopped taking it after about 6 days because I started feeling pressure/ heaviness to the left side of my heart/chest . When I was taking it I would only eat about 700-900 calories a day, Now that I'm off it I don't know how much calories to eat to lose weight. Today I ate about 1100 calories and burn about 170 on the elliptical. I want to go back to take phetermine, but I'm scared something bad might happen to me. what should I do?