Considering the vagueness of the rules, I believe that the best method is to do what the person above said. There are hundreds of books in the library or online for density, buoyancy, concentration, etc.
I have a question '~'
To 2.00 L of 0.445 M HCl, you add 3.88 L of a second HCl solution of an unknown concentration. The resulting solution is 0.974 M. Assuming the volumes are additive, calculate the molarity of the second HCl solution.