voi nota ms=masa de solutie
md=masa dizolvatului
c=concentratie
ms1=800ml
c=20% => md=c*ms/100=20*800/100=20*8=160g
md=160g
c=10% => ms2=md*100/c=160*100/10=160*10=1600ml
mapa=ms2-ms1=1600-800=800g
raspusul este a)800g
