[tex] \frac{c}{100} = \frac{md}{ms} \\ \frac{10}{100} = \frac{md}{400} [/tex]
[tex] \frac{1}{10} = \frac{md}{400} [/tex]
[tex]md = \frac{400}{10} = 40g[/tex]
[tex] \frac{c}{100} = \frac{40 + 20}{400 + 20} [/tex]
[tex] \frac{c}{100} = \frac{60}{420} \\ c = \frac{100 \times 60}{420 } \\ c = \frac{10 \times 60}{42} \\ c = \frac{600}{42} [/tex]
c=14,28%
Sper că te-am ajutat si baftă in continuare! :D