What is the normal amount of time to loose weight and get a flat stomach?

I am not overweight a lot, I just need to lose like 10-15 pounds. I don’t have a gut, but you can see I have some extra pounds if I am going shirtless. I am 19 years old, my height is around 5’8, and I weight 180. How long should it take for me to loose all the weight and get a flat stomach?