2kg=2000g
100.......10
2000....x1
x1=200 g solut in prima solutie
100........25
800.......x2
x2=200 g solut in a doua solutie
x3=100 g solut
x1+x2+x3=200+200+100=500 g solut folosit
2000+800+100=2900 g masa solutie
c=m solut/m solutie*100=500/2900*100
c=17,24%