md=20g
m,apa=180g
ms= md+m,apa= 200g
c= mdx100/ms= 20x100/200=.10%
c2= 3c1=30%
30/100= 20/ms2----> ms2=66,66g----
m,apa evaporata=ms2-ms1=66,66g-200g=.....................calculeaza
c3=3c1=30%
30/100=(20+md)/(200+md) , deoarece masa de sare adaugata mareste si md si ms......calculeaza !!!