Question

Am gaina albe si negre:2/5 dintre ele sunt albe si 15 sunt negre.Cate gaini am in total?

Answer 1

5/5-2/5=3/5
15:3x5=5x5=25(gaini)

Answer 2

$x+y=z$
$\frac{2}{5}z=x$
$y=15$
$\frac{2z}{5}+15=z$
$\frac{2z}{5}+\frac{75}{5}=\frac{5z}{5}|*5$
$2z+75=5z$
$3z=75$
$z=\frac{75}{3}$
$=>z=25$