Question

Andra , Ionut si Crina au in total 90 timbre. Andra si Ionut au imreuna 53 timbre iar Ionut si Crina au impreuna 65 timbre. Vate timbre au fiecare? Rezolva in trei moduri, afland mai intai : a) numarul timbrelor Andrei, numarul timbrelor lui Ionut, numarul timbrelor Crinei.

Answer 1

a+b+c=90 ; a=Andra; b=Ionut; c=Crina
a+b=53
b+c=65
1.
a+(b+c)=90
a+65=90
a=90-65
a=25;
a+b=53
b=53-25
b=28
b+c=65
c=65-28
c=37

2.
a+b+c=90
a+b=53
b+c=65
53+c=90
c=90-53
c=37; b=65-37; b=28 ; a= 53-28; a=25
3.
a+b+c=90
a+b=53⇒ a= 53-b
b+c=65⇒c=65-b
53-b +b+65-b=90
118-90=b
b=28
a=53-28; a=25;
c=65-28; c=37