c=md/ms×100
ms=md+m apa
10/100=30/30+m apa
100×30=10(30+m apa)
3000=300+10 m apa |-300
2700=10 m apa |÷10
m apa= 270 g
soluria sa isi dubleze concentratia => c=20%
20/100=30/30+m apa
30×100=20(30+m apa)
3000=600×20 m apa |-600
2400=20 m apa |÷20
m apa=120 g
masa apei ce trebuie evaporata= 270g-120g=150g
