Răspuns :
[tex] \frac{0,2x}{4} = \frac{1}{5} => \frac{ \frac{2}{10}x }{4} = \frac{1}{5} => \frac{ \frac{x}{5} }{4} = \frac{1}{5} => \frac{x}{5}: \frac{1}{4} = \frac{1}{5} => \frac{x}{5} * \frac{4}{1} = \frac{1}{5} => [/tex][tex] \frac{4x}{5} = \frac{1}{5} => 4x*5=5=> 20x=5 =>x=4[/tex]