Question

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

Answer 1

5/5=intregul. 
2/5=gaini albe
1/5=? 
/---/---/---/---/---/->2/5 gaini albe
/---/---/---/---/---/->15 gaini negre
/---/---/---/---/---/->1/5 din 15=15:5*1=3. 
3*2=6 gaini albe
15+6=21 gaini am in total.

Answer 2

x.......... 2\5 gini albi
y.......... 15 gini negre
x+y= 2\5+ 15= 10\5+75\5 | x5
                     = 10+75=85 gaini sunt total