md=c*ms/100=10*200/100=20g sare
ms=md+mapa => mapa=ms-md=200-20=180g apa
daca se evapora 20% => ramane 80% din cantitatea apei
80*180/100=144g apa
md=mdf caci sarea nu se evapora
msf=mdf+mapafinala=20+144=164g solutie
cf=mdf*100/msf=20*100/164=12,195%