[tex]a) \frac{a}{2} = \frac{b}{3} = \frac{c}{5} =k=>a=2k;b=3k;c=5k\\
\frac{a}{2} = \frac{c}{5}=>a= \frac{2c}{5} =>a=\frac{40c}{100}=\frac{40}{100}\cdot c\\
a=40\%\ din\ c\\ [/tex]
[tex]b)(a-b)^2 +(b-c)^2+(c-a)^2=56\\
(2k-3k)^2+(3k-5k)^2+(5k-2k)^2=56\\
k^2+4k^2+9k^2=56\\
14k^2=56\\
k^2=4\\
k=\pm \sqrt{4}=\pm2\\
k\in N=>k=2\\
a=2k=4\\
b=3k=6\\
c=5k=10
[/tex]
