Question

Ancuta are 36 de timbre romanesti si straine
Stiind ca timbrele romanesti reprezinta intreitul celor straine
Cate tinbre de fiecare fel are Ancuta?

Answer 1

r+s=36;
⇒r=3s;
⇒3s+s=36
⇒4s=36⇒s=9[timbre straine];
⇒r=27[timbre romanesti];

Answer 2

 t,r  /......../......./....../
ts   /......../
in total 36 timbre
cat reprezinta o parte?
36 : 4 = 9
cate timbre romanesti are?
3 x 9 = 27
cate timbre straine are?
1 x 9 = 9

algebric
r + s = 36
r = 3 s
3s + s  36
4s = 36
s = 36 : 4
s = 9
r = 3xs
r = 3x9
r = 27