What is the percentage of HP that an enemy Pokemon will have after Spikes damage and Super Fang?

Question

I need help calculating. And not only full spikes, I want the calculation with 1 layer of spikes, the calcualtion with 2 layers of spikes, and the calculation with 3 layers of spikes.

Answer 1

1 layer of spikes (100-12.5)x0.5= 43.75% left
2 layers of spikes (100-18.75)x0.5= 40.624% left
3 layers of spikes (100-25)x0.5= 37.5% left

Comments

You're right, I screwed up in my math.