It's the same. Any time you add two juices together with the same nicotine content, it'll always stay the same.
But because you might want to dilute in the future, I'll show you how to do it. First I'll explain how to do this with two equal volumes of liquid. Say you have 10ml of 24mg
juice, and 10ml of 16mg
juice. You just take the average of the two juices. Add them together, 24+16= 40. Then divide by how many numbers you just added. 40/2=20. So you'd end up with 20ml of
juice that is 20mg nicotine.
Now, for juices that you have different mls of, it's pretty much the same, you just have to break them down to common denominators. Say you have 15ml of 24mg juice, and 10ml of 16mg juice. You can't just add those two numbers together and divide by two, that would be extremely inaccurate. First you break them down. The biggest number that both 15 and 10 go into is 5, so you're going to break your juices down in increments of 5 (only on paper, you don't have to actually break them down during the mixing process).
So you have increments of 5ml of 24mg juice, 5 ml of 24mg juice, 5ml of 24mg juice, 5ml of 16ml juice, and 5ml of 16mg juice. You add all of your mg increments together. 24+24+24+16+16=104, or (24*3)+(16*2)=104 if you prefer the shorthand, multiplication method. Now you just divide your total by the number of times you added (or the sum of the numbers your multiplied by in the multiplication method). 104/5=20.8. So you'd end up with 25ml of 20.8mg juice.
It's really basic math once you're familiar with, and this might come in handy in the future!