In 14 weeks it is highly unlikely you will gain 3lbs of muscle whilst reducing bodyfat by 4%.

Whether or not you can lose the 4% solely depends on how much you weigh.

edit - I have just read that you are only 15 years old. Forget about losing bodyfat. Just eat a clean diet and you can start to weight train at 15 without any issues as long as you are instructed properly.