Finding Molarity of Evaporated substance!

A puddle evaporates 29% of initial volume . What's the Na+ after evaporation of the initial 0.449 M? 


really don't get how to do this! I tiried doing m1v1=m2v2 while setting it to v1=1L and v2=0.29L but it is wrong.


Can someone explain this to me please?


 If you had 1 L to begin with and the concentration 0.449moles per litre, you will still have 0.449 moles at the end but the volume with be 0.29L. So 1 Litre of this would contain 0.449/0.29 = 1.55M