If you have to ask how to dilute one drop into three, you probably shouldn't even have gotten something like that anyways, TBH... no offense, it's just something so easy that anyone dealing with that concentration should know how to handle it.
------------->If it's one drop, add 2 more to it and that's 3. Simple math.
Make sure you "wash" the container out after it's empty, there will prob. be ~100mcg left in it. Don't use tap water
Or you could add 3ml of distilled water to the drop, and each dose 1ml...
It's probably like 250mcg... People have huge misconceptions about LSD strength today. An average hit of "good" blotter today is ~50-60mcg...