I'm a 16 year old girl and I weigh 146 pounds. I'm 5 ft tall and I've been trying to lose weight. My only exercise is from PE. How much should I weigh?

Weight control. Your "normal" weight would be around 120. The best thing to do is not to focus on the number, but focus on getting and keeping healthy habits. Do an hour a day of exercise on most days. Eat more healthy choices and avoid high fat, high sugar foods. Watch your portions and don't overeat. Slow steady changes will help you lose the weight and keep it at a "normal" range.