How do I loose 12 pounds? And 3 inches off my waist?

Right now I'm 99lbs, 45 kg or 7.285 stone.
I really really want to loose 12 lb.

How do I do it? I'm almost 15. Will it be easy?

Right now I'm 32" 24" 34" and I want to be

29" 21" 31"

right now I'm a size XS. And my clothing size is 0-2 (us)

I'm 5'2", 1.57 m, or 157 cm
How do I loose 12 pounds? And 3 inches off my waist?
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