BIOLOGY HELP PLEASE question?

Get a container with semipermeable membrane. Put in A on one side and known 0.4M solution. If the water level increases on the A side, then you know that A is more than 0.4M. If it stays the same, then it's 0.4 M solution. If the water level decreases, then it's 0.2 M. Try with different types of known Molarity for others, until you can pinpoint which solution it is.