[Lucy_K5]

I will list everything that is given and set as (Given:)

So I measured a mass of compound A, lets say 15mg. And I measure a mass of compound B, lets say 6mg. (Given: concentration of each compound is 20mg/mL). Compound A is measured in excess. So using the mass, and the given concentration, I calculate the volume required for each compound(using the given concentration of 20mg/mL) and mix each compound into their required volumes to create 2 solutions. However, (Given: 10% molar percent[that is to say 10% of the total number of moles in the final solution]) of Compound A, what is the mass of Compound A that I need to add to Compound B in order to get that mole percent? However, I cannot change the total concentration of the solution(Given: 20mg/mL)

[Borek]

Sorry, this is pretty chaotic. Can you start by explaining what it is that you are trying to achieve in general? You have listed a lot of petty details without saying what is the general picture.

[Vidya]

so what is the question actually?