vas de apa= v
[tex] \frac{3v}{4} [/tex] se pune
[tex] \frac{3v}{4} [/tex] - [tex] \frac{2}{5} [/tex]= 90 => [tex] \frac{3v X 5}{20} [/tex] - [tex] \frac{4 X 2}{20} [/tex]=90 => [tex] \frac{15v-8}{20} [/tex]=90 => 15v-8= 90x20 => 15v-8= 1800 => 15v=1808 => v= 120,5(3)
Nu cred ca e corect...
