Question

Ana si Bogdan au impreuna 7 mere , iar Ana si Calin au impreuna 8 mere. cate mere are Aba stiind ca impreuna cei 3 copii au 12 mere.

Answer 1

Ana are x mere.
Bogdan are y mere.
Calin are z mere.

x+y=7
x+z=8
Adunam relatiile si obtinem 2x+y+z=15 (1)
x+y+z=12 (2)
Din relatia (1) scad relatia (2)
(2x+y+z)-(x+y+z)=15-12
x=3
Deci Ana are 3 mere.

Answer 2

a+b=7[mere];
a+c=8[mere];
a+b+c=12[mere];
⇒c=12-7
⇒c=5[mere-Calin];
⇒a=8-5
⇒a=3[mere-Ana];
⇒b=4[mere-Bogdan];