Safe weight loss is considered to be 1-2 pounds/week, which would come out to 4-8 pounds/month. 10 pounds in 3 months, might be a bit much, but if you watch portion sizes and get plenty of exercise, you could do it. Anything drastic, such as diet pills, skipping meals, over exercising, etc, would be unsafe.
Be sure to adopt lifestyle changes, otherwise, weight will most likely be regained quickly.
It depends on your body type, height, weight etc... Most doctors would say it is unhealthy (I'm not a doctor...) so be careful with drastic measures. Can it be done? Yes. Is it risky? Yes. Listen to your body, it will tell you whether it's doing OK or not. And make sure to get plenty of nutrients in your diet! :-)
6 small meals/day to keep the metabolism going
Carry a meal/snack box every where you go
Use shakes/bars (Slim Fast, Southbeach, etc.) as backup when food isn’t readily available
3 dairy items a day to increase metabolism
Never – ever! – skip a meal
Drink plenty of water or sugar-free beverages
Cardio exercise 6 days/week at least 30 minutes
Target all 6 muscle groups during resistance training at least once/week for 15 minutes each minimum
Eat out only once/week