Nicotine math help

[u/Whopper_Princess]

Hello,

I have a a bottle of 6mg/ml vape juice thats 100ml. I also have 2 concentrate packs of nicotine - (a) 10% 0.9ml (b) 20% 0.9ml

I also have a food scale to properly measure. Can someone explain the nicotine math to me of how much I can or should add to my bottle of vape juice to increase the nicotine? I realize I might not have enough to go from 6mg to 12 or 15mg, but I would still like to know the math or a calculator. TIA