at 20 degree celcius, the solubility of a solid substance x in water is 42g/L. There are 3 solutions containing x kept at this temperature: S1 5.1g/L, S2 contains 39g/L, and S3 contains 57g/L. if we want to make S1 saturated with x, is it possible that we can add an equal volume of S2 and S1 because the overall concentration will become about 44g/L. or is it we must add more S2? what equation should I use?