c3= md3x100/ms3
ms1=1000g(consider ro=1g/ml)
c1= 40%-------------------------------> md1= c1xms1/100= 0,4x1000= 400g
ms2=?
c2= 70%-------------------------------> md2= 0,7xms2
c3=md3x100/ms3, md3=md1+md2
ms3=ms1+ms2
50/100= (4oo+0,7ms2)/ (1000+ms2)
100(400+0,7ms2)= 50(1000+ms2)--------------------> calculeaza ms2!!